# User manual | TI-83 Graphing Calculator Manual ```Graphing Calculator Manual
TI-83
Kathy V. Rodgers
University of Southern Indiana
Evansville, Indiana
to accompany
Trigonometry, 5th Ed.
Charles P. McKeague and Mark Turner
Preface
Technology, used appropriately, enhances the teaching and learning of
mathematics. The purpose of this manual is to provide sequences of keystrokes
for developing calculator skills, to assist students in interpreting calculator
screens, and to relate the capabilities of technology with students’ analytical
skills.
The ultimate goal is to deepen the students’ understanding of
trigonometry and its application to problem solving.
How to use this Manual.
Anytime you are asked to complete a command that is in capital letters, then you
are being asked to press a specific calculator key. For example if the directions
say ENTER then you should press the ENTER button on your calculator;
however, if the directions ask you to enter 4, then you are being asked to enter
the number 4--press the 4 key. After you are given a sequence of keys to press,
you will be given a calculator screen to compare with the screen of your
calculator.
Alert or Note
ALERT will be used when caution needs to be exercised when using the
1
calculator. For example,
, cannot be entered in the calculator as 1/2x.; the
2x
1
calculator would interpret this as x . Hence you would be alerted that you must
2
use parentheses and enter this as 1/(2x). The word Note will precede additional
information or the interpretation of a calculator screen.
Explanation of Exercises from the Text
Actual problems from the text are worked in this manual. Each section will be
identified and the specific problem number will be in bold print. Every time a
problem from the text is discussed, the necessary calculator skills are explained
as well as the necessary analytical skills. After completing the problem the
student is encouraged to interpret and to check the answer.
Keyboard Layout
Study the face of your calculator. Notice how the keys are grouped by color.
Also take note that there is yellow and/or green (blue for the TI-86) writing above
Rodgers, K.
each button; also note there is a yellow key and a green key on the upper left of
the key pad. If you wish to access any of commands or symbols written in yellow
you must first press the yellow key; if you wish to access any of the letters or
symbols written in green (blue), you must first press the green key. The blue
keys down the side are your operation keys, the blue keys(TI-83) across the top
relate to graphing, and the blue arrow keys let you move the cursor on the
calculator screen.
Screen Brightness
Turn your calculator on. Is the screen too dark or too light? If you are not
satisfied with the brightness of your calculator, press 2nd and use the up or down
blue (gray) arrows to either make your screen darker or lighter. (Do not hold the
2nd key down; press 2nd, release this key, and then press the up or down blue
arrow.) You will see a number appear briefly in the upper right corner of the
calculator screen, this is the brightness setting which ranges from zero to nine. If
your screen is still dim when the number nine is showing, you may need new
batteries.
The author has written this manual with the specific goal of enhancing
understanding and minimizing calculator magic (pushing buttons until an answer
magically appears). If you have questions or comments, the author may be
reached at the address given below.
Kathy V. Rodgers
Department of Mathematics
University of Southern Indiana
8600 University Boulevard
Evansville, IN 47712
email: [email protected]
ii
Contents
Preface
i
1
The Six Trigonometric Functions
1
2
Right Triangle Trigonometry
11
3
Radian Measure
22
4
Graphing and Inverse Functions
35
5
Identities and Formulas
68
6
Equations
74
7
Triangles
90
8
Complex Numbers and Polar Coordinates
94
A
Quadratic Programs
101
iii
Chapter 1
The Six Trigonometric Functions
Section 1.1
Calculator skills needed for this section include the exponent key and the square root
key. Practice the following examples before attempting to work problem 25.
To raise 6 to the second power complete the following keystrokes.
press 6
press
x2
You will find the
column.
x2
button in the middle of the left
press ENTER
There is a second method for squaring six. Use the following keystrokes. Learning these
key strokes is important if you wish to raise a quantity to some power where there is not a
special key such as the x 2 key.
press
press
press
press
6
^
2
ENTER
To find the square root of 36, press the following sequence.
2
press
To access the
, press 2nd and the x key.
enter 36
close the parenthesis
(In this particular case, closing the parentheses does
not matter; however, it is best to develop the habit of
closing all parentheses.)
Rodgers, K.
1
Chapter 1
TI-83
press ENTER
A second way to find the root of a number is to write the expression in exponential form.
1
36 2
Enter this in your calculator and check the screen that follows to verify your work.
To find the answer to question 25, complete the following sequence of steps.
enter 3
press x
press +
press 4
2
2
press x
press ENTER
press
press ANS
press ENTER
To access the ANS key press 2nd and (-).
You could complete this problem in one step by first solving for c. Your paper-pencil
work should resemble the following.
Rodgers, K.
2
Chapter 1
TI-83
c 2 = 32 + 42
c = 9 + 16
c = 25
c=5
The calculator keystrokes to mirror this work are:
press
enter 32 + 42 )
press ENTER
Section 1.2
To prepare your calculator for graphing functions
press MODE
The settings on the left should all be dark.
To change settings, move the cursor until it is flashing on the setting that you need and
then press ENTER.
Press CLEAR or QUIT and this will you return to the home screen.
Problem 13 asks you to graph 3x + 2y = 6 .
First solve this equation for y to get y =
press Y =
−3
x +3 .
2
One of the five blue menu keys on the top row of your
calculator.
3
Chapter 1
TI-83
press WINDOW
enter -4.7 for Xmin
enter
enter
enter
enter
enter
enter
4.7 for Xmax
1 for Xscl
-5 for Ymin
5 for Ymax
1 for Yscl
1 for Xres
There is a reason for selecting a minimum x-value of 4.7 and a maximum x-value of 4.7. The difference
between 4.7 and -4.7 is 9.4. The number of pixels is
9.4
is 0.1. This setting makes the x-values
94 and
94
increase by 0.1 as you trace along the graph. You will
see these values or some multiple of these values
used throughout this manual.
You will want to leave the x resolution set on one most
of the time. You are telling the calculator to light all of
the pixels. If you entered a two, you would be telling
the calculator to light one pixel out of two.
press GRAPH
The following are calculator screens for Y=, for the window settings, and the graph Y1 .
Note: The calculator really does not care if you simplify the expression. You would have
(6 − 3 x)
gotten the same answer had you entered y =
. However, you must use the
2
parentheses around the numerator; otherwise the calculator will only divide the
last term by 2.
The calculator permits you to scroll along the graph.
press TRACE
press the right blue arrow
Rodgers, K.
4
Chapter 1
TI-83
Note. As you trace along the graph, the coordinates of the highlighted point are
displayed on the bottom of the calculator screen. In the preceding example, the
cursor is flashing on a point with the coordinates of (2.4, -.6). In the upper left
corner of the screen, you will see the function displayed that was entered in Y1 .
After selecting TRACE if you do not see the function displayed in the upper left
hand corner, go to FORMAT (above the blue zoom key) and select ExprOn.
The calculator permits you to view a table of values, much like a t-table created manually.
press TBLSET
enter 0 for TblStart
enter 1 for ∆Tbl
press TABLE
To access TBLSET, press 2nd and WINDOW
∆ Tbl (read delta table) is asking by what increment
you want the x-values to increase. For example, if you
enter 1, each x-value will differ by one, if you enter two,
each x-value will differ by two.
To access TABLE press 2nd and GRAPH
Note. You may use the up and down blue arrow keys to scroll up and down the table.
Remember, the values you see in this table are the coordinates of points on the
graph of the function you entered in Y1 .
Alert! Question 16 asks you to graph a vertical line. Remember that a vertical line is
not a function. As long as your graphing utility is in function mode, you cannot
use the graphing utility to graph this line. However, this is an easy graph to
create using paper and pencil. This problem says that x must be 3 and that y can
be any number. Hence the following ordered pairs are all on this graph: (3,0),
(3,-1), (3,2) etc.
Your calculator will draw, but not graph a vertical line for you. Clear Y1 and use the
following keystrokes.
press GRAPH
press DRAW
select VERTICAL
To access DRAW, press 2nd and PRGM.
Use the down blue arrow until the cursor is
flashing on Vertical and then press ENTER or
simply press the number 4.
Press the right blue arrow until the x-value on the bottom of the screen is 3.
5
Chapter 1
TI-83
Note. If you press ENTER, the vertical line will stay where you have placed it and you
may draw a second vertical line by using the right and left blue arrow keys.
Alert! When you use the DRAW feature of the calculator, you cannot use the TRACE or
the CALC features of the calculator. If you use the blue arrows, you have a free
floating cursor that is not locked to the line.
Alert! To remove the vertical line press DRAW and select ClrDraw and ENTER.
Question 25 asks you to graph the circle defined by the equation x 2 + y2 = 25 . Once
again, you must first solve for y. Do the following paper-pencil work before trying to enter
this in your calculator.
y 2 = 25 − x 2
(
y = ± 25 − x
2
)
The calculator does not have a ± key; you will have to enter this in your calculator as two
different expressions.
press Y =
enter
−
( 25-x ) in Y
( 25 − x ) in Y
2
1
2
2
press Graph
Alert! Does your circle look more like a football than a circle? Do you even have a
complete circle? Try the following WINDOW settings.
press WINDOW
Rodgers, K.
Your minimum and maximum values must be
greater than 5 since the radius of the circle is
5. A -9.4 and 9.4 were chosen as the minimum
and maximum x-values because they are
multiples of 4.7 as was explained earlier.
6
Chapter 1
TI-83
press ZOOM
The middle blue key on the top row.
press 5 for ZSquare
You will notice that the viewing window is
rectangular, the zsquare changes the x and y
window settings to an approximate 3 to 2 ratio.
Note. You may have a gap between the two circles. This is due to the resolution.
When you sketch this on your paper, be sure to connect the two semicircles.
Instead of entering −
Enter
(25 − x ) in Y
2
1
(25 − x ) in Y
2
2
as before; however in Y2 enter - Y1.
press Y=
select Y2
press
press
select
select
select
press
you could do the following.
VARS
Y-VARS
FUNCTION
Y1
ENTER
Move the cursor to Y2 and if you have
something in Y2 , press CLEAR.
The negative key, not the subtraction key
Note. The real benefit of this procedure is that you can very easily graph a
second circle by only changing the entry in Y1 .
7
Chapter 1
TI-83
Question 29 asks you to graph x 2 + y 2 = 1 . If you had used the method described above,
then you would only have to enter 1 − x 2 in Y1 . Since Y2 is - Y1 this will graph the bottom
half of your circle. Question 29 is asking you to use the TRACE feature of the calculator
to find all ordered pairs that have an x-value of 12 .
press TRACE
enter 12
There is no need to use the blue arrows.
The directions say to write your answer as an ordered pair and round to four places past
the decimal point when necessary. Certainly this should not be difficult for you to do;
however, the calculator will do this for you.
select
go to
press
MODE
FLOAT and use the right arrow until the cursor is blinking on the 4.
ENTER
You will notice that there are only three decimal places instead of four; the fourth number
was a zero, hence not a significant digit.
Problem 39 asks you to find the distance between the points (3,7) and (6,3).
Using the distance formula you have d = (3 − 6) 2 + (7 − 3)2 . After you have simplified
this, you could use your calculator to verify your answer.
press
enter (3 − 6)2 + (7 − 3)2 ))
press ENTER
Rodgers, K.
8
Chapter 1
TI-83
If you want your calculator to draw the triangle described in problem 83, perform the
following keystrokes. (It is probably easier to perform this task by hand.)
press
select
press
press
DRAW
Line(
ENTER
0,0,5,0)
press :
press
select
press
press
press
select
press
press
press
DRAW
Line(
5,0,5,12)
:
DRAW
Line(
5,12,0,0)
Y=
WINDOW
Select Line( by pressing 2 and ENTER.
The calculator understands that these
numbers represent the two endpoints of the
line segment.
To access the colon, press ALPHA and the
period key.
Clear all functions.
You know the least x-value is zero and the
greatest x-value is 5. Choose a value less
than zero for the minimum x-value and a value
greater than 5 for the maximum x-value. The
least y-value is zero and the greatest y-value is
12. Select a number less than zero for the
minimum y-value and a number greater than
12 for the maximum y-value.
press ENTER
Note. Remember, the TRACE feature does not work with the DRAW feature. You can
use the right and left blue arrows to move the floating cursor around the screen;
however, this cursor is not locked to the graph.
Alert! The only way to clear this triangle is to go to ClrDraw. You access this by
pressing DRAW and selecting number 1 and pressing ENTER.
9
Chapter 1
TI-83
Section 1.3
Question 25 asks you to find sin θ and cos θ if the point ( 9.36, 7.02 ) is on the terminal
side of θ . Recall that the sin θ =
enter 9.36
press STO
enter x
press
enter
press
enter
press
y
and that r = x 2 + y 2 .
r
This is the key above the ON button.
You may either use the X, Y, θ, n button or the
green x above the STO key.
ENTER
7.02
STO
y
ENTER
(x 2 + y 2 )
enter
press STO
enter r
press ENTER
y
press SIN  
r
Section 1.4
Question 9 asks you to find csc θ given sin θ = 54 . Recall that csc θ =
Certainly you could find this answer by simplifying
1
4
5
1
.
sin θ
. You could also use the following
keystrokes.
enter
( 54 )
press x −1
press ENTER
This key is above the x 2 key.
Rodgers, K.
10
Chapter 2
Right Triangle Trigonometry
Before beginning the exercises in Chapter 2, set your calculator in degree mode.
press MODE
select Degree
press ENTER
press CLEAR
Use the down and right blue arrows until the cursor is
flashing on degree.
The degree setting is not selected until you push
ENTER even though the cursor is flashing on degree.
CLEAR returns the calculator to the HOME SCREEN.
QUIT also returns the calculator to the HOME
SCREEN.
Example: To find the sin16 perform the following keystrokes.
press SIN
enter 16
press ENTER
.
Note. It is not necessary to use the degree symbol if you are in degree mode. If
you had used the degree symbol, your answer would not have changed.
Compare your calculator screen with the calculator screen that follows.
If you are not in degree mode then you must use the degree symbol. For
the following, the calculator was not in degree mode. The screen on the
left gives the answer using the degree symbol and the answer is correct.
The screen on the right does not show the degree symbol being used and
the answer is incorrect.
11
Chapter 2
TI-83
Note. You could also omit closing the parentheses since you are at the end of
an argument. If you do not close the parentheses, the calculator
automatically assumes it to be at the end of the expression. It is best
to develop the habit of closing all parentheses.
Section 2.1
Question 17 asks you to find the sin 10 using the Cofunction Theorem.
Review the Cofunction Theorem from your text. This theorem says the sin 10 is
equal to the cos 80 . To complete this on your calculator use the following
keystrokes. (Your calculator should be in degree mode.)
press COS
enter 80
press ENTER
For your own information now find sin 10 .
press SIN
press 10
press ENTER
This is an example of the Cofunction Theorem. The cos 80 is equal to the
sin 10 .
Suppose you wished to find the sin 39.8 using the Cofunction Theorem. The
calculator will find the complement for you.
press COS
enter (90 - 39.8)
press ENTER
Rodgers, K.
12
Chapter 2
TI-83
(
Question 29 asks you to find 2cos 30
).
2
It is important to know how to
correctly use parentheses when entering an expression raised to a power.
press (
press 2
press COS
enter 30
press ))
press ^
press 2
press ENTER
You could enter the * symbol between 2 and
COS; however it is not necessary.
You could also use the x 2 key.
Compare your screen with the screen that follows.
Note. Compare the following.
sin 2 30
( sin
sin
)
( 30 )
30
2
o 2
The first two expressions are equal. You are to find the sin 30 and then square
the answer. The last problem is asking you to find sin 900 ( 302 = 900 ). The
answers to the first two are the same; the answer to the third problem is different.
Note the calculator screen that follows.
2
Note. The calculator will not let you enter sin 30 ; this must be entered as
(sin(30))2 .
Rodgers, K.
13
Chapter 2
TI-83
Problem 31 could be entered in the calculator in one step. Try it. Compare your
answer with the calculator screen that follows. Did you correctly insert the
parentheses?
Question 50 asks you to find the cotangent of an angle. If you search and
search, you will not find a cotangent key on your calculator; however, you can
still complete this question by using your knowledge of reciprocal identities. The
1
cot θ =
.
tan θ
To complete question 50, use the keystrokes that follow.
enter
press
enter
press
1
÷
(TAN (30))
ENTER
Section 2.2
Question 1 asks you to add the measures of two angles. First recall that
1 = 60 ′ and 1′ = 60′′ . Your paper-pencil work should resemble the following.
37 +26 = 63
45′ + 24′ = 69′
Change 69′ to 1 9′
63 +1 = 64
Final Answer 64 9 ′
To complete this same problem on the calculator, use the following sequence of
keystrokes.
enter 37
Rodgers, K.
14
Chapter 2
TI-83
press ANGLE
select the degree symbol
enter 45
press ANGLE
select the symbol for minute
press +
enter 26
press ANGLE
select the degree symbol
enter 24
press ANGLE
select the symbol for minute
press ENTER
Your screen returns 64.15 , but you want your answer in degrees and minutes.
You could convert the .15 to minutes by simply multiplying 0.15 times 60 to get 9
minutes. However if you will follow these keystrokes, your calculator will give the
answer in degrees, minutes and seconds.
press ANS
press ANGLE
select DMS
press ENTER
To recall your previous answer.
DMS--degrees, minutes, seconds
You could perform this task in one step by pressing
ENTER.
DMS before you press
Question 15 asks you to convert from decimal degrees to degrees and minutes.
Use the skills you learned in the previous example to answer this question.
enter 35.4
press ANGLE
select DMS
press ENTER
Rodgers, K.
15
Chapter 2
TI-83
Question 23 asks you to convert from degrees and minutes to decimal degrees.
Your paper-pencil work should include the following.
45 +
12
= 45.2 .
60
Calculator strokes to mirror this work would be:
enter
press
enter
press
enter
press
45
+
12
÷
60
ENTER
However, your calculator will perform this for you in one step.
press
press
select
press
press
select
press
45
ANGLE
degree
12
ANGLE
minute
ENTER
Note. The directions ask you to round the answer to the nearest hundredth of a
degree. Yes, your calculator will also do this.
press MODE
Move the cursor down until it is flashing on float and to the right
until it is flashing on the 2.
press ENTER
press QUIT
This will return you to the Home Screen.
Rodgers, K.
16
Chapter 2
TI-83
All of your answers will be rounded to hundredths place; however, it is probably
easier to simply use your own knowledge to perform this task.
Question 31 asks you to find the sin 27.2 . Before entering this in your
calculator, verify that you are in degree mode. Since you set your calculator to
two decimal places for the previous problem, all answers will be rounded to
hundredths until you reset the calculator to let the decimal point float.
Question 51 asks you to complete a table comparing sin x and csc x . Practice
the following keystrokes until you have mastered this calculator skill.
press Y =
enter SIN in Y1
This key is one of the blue keys on the top row.
enter 1/SIN(x) in Y2
Recall csc x =
1
.
sin x
press TBLSET
To access the TBLSET press 2nd and WINDOW, a
blue button on the top row next to the Y = button.
enter 0
The cursor will be flashing on the number following
TblStart. Since you want your x-values to start at
zero enter a zero for TblStart (table start).
select ∆ Tbl
Use the down cursor to select ∆ Tbl , the symbol for
delta table. Delta is used in mathematics to mean
change.
Rodgers, K.
17
Chapter 2
TI-83
enter 15
You are telling the calculator that you want the first xvalue to be zero and the second x-value to be 15, and
the third to be 30, etc. In other words, you want the xvalues to increase by 15 each time.
Note. Select Auto for both the independent and dependent variables.
press TABLE
To access TABLE use 2nd GRAPH.
Your screen should resemble the following calculator screen.
.
Notice the ERROR in Y2 . You asked the calculator to divide one be zero which
is impossible. The calculator tells you this by displaying the word ERROR.
Recall that you entered sin x in Y1 and 1/sin(x) in Y2 . In previous mathematics
classes you learned that a number times its reciprocal is 1. Go to Y = and in Y3
enter Y1 ∗ Y2 to investigate what happens when a trigonometric function is
multiplied by its reciprocal. Use the following keystrokes.
press Y =
select Y3
press VARS
select
select
select
press
press
select
select
select
press
Rodgers, K.
Y-VARS
function
Y1
*
VARS
Y-VARS
function
Y2
TABLE
This button is found to the left of the CLEAR
key.
Use the right cursor to make this selection.
Symbol for multiplication.
Use the right cursor until you can see Y3 . All
entries in this column are 1 except when x = 0.
18
Chapter 2
TI-83
The ERROR in Y3 is the result of trying to
divide by zero which is impossible.
Note. By looking at this column, you observe the relationship between sin (x)
and csc (x).
press QUIT
This will return you to the Home Screen.
Question 55 asks you to find θ given that the cos θ = 0.9770 . To solve this
problem, you will need the inverse cosine key θ ,which is the key that will give you
the value of θ when you know the value of the cosine.
press cos −1
enter 0.9770
press ENTER
This is above the COS button.
The directions ask you to round your answer to tenths.
Note. The first answer is in radians; the second answer is in degrees.
Check your answer by finding the cosine of each answer.
Section 2.3
Question 1 asks you to find the length of side a, given angle A is 42° and side c
is 15 feet. (From the directions you know you have a right triangle ABC with a right
angle C.)
To find a, you could use the formula for sin A .
Rodgers, K.
19
Chapter 2
TI-83
a
c
a
sin 42 =
15
15sin 42 = a
sin A =
Using calculator skills you learned from the previous sections, enter this
information on one line in your calculator. Your screen would look like the
following.
Interpret your answer. Side a is 10.04 feet in length.
After you have worked Question 57, model the problem using your graphing
calculator. This sequence of keystrokes graphs a circle to represent the Ferris
wheel by using parametric equations. The calculator is plotting a series of points
(x,y) where the x-value is defined as cos x and the y-value is defined as sin x. To
change the size of the circle, multiply by 98.5, the radius of the circle. The
center of the Ferris wheel is at the origin, this means the bottom half of your
Ferris wheel is below the x-axis. A positive vertical translation of 98.5 feet would
put the bottom of the Ferris wheel on the x-axis, but this would not make the top
of the wheel 209 feet above the ground. We need to translate up another 12 feet
or a total of 110.5 feet. Try the following.
press
select
press
press
press
press
press
select
MODE
PAR
PAR stands for parametric
ENTER
Degree
ENTER
CLEAR
Y=
X1T = and enter 98.5 cos (T)
The T button is to the right of
the alpha key.
select Y1T = and enter 98.5 sin (T) + 110.5
press WINDOW
Tmin = 270
By making the minimum value of T = 270, you are
set
set
Rodgers, K.
Tmax = 630
telling your calculator to start evaluating x and y at
the point where the Ferris wheel is closest to the
ground.
Select 630 because this is the sum of 270 and 360,
the number of degrees in a complete circle.
20
Chapter 2
set
TI-83
Tstep = 5
This is an arbitrary number. If you choose a very
small number the calculator would move very slowly;
if you were to choose a very large number, your circle
would have sharp edges. When you set the T-step at
five, you are telling the calculator to plot a point every
five degrees.
Continue with the following settings.
Xmin = −246
Xmax = 246
Xscl = 0
Ymin = −25
Ymax = 300
Yscl = 0
press GRAPH
press TRACE
Compare your graph with the screen that follows.
Note. The cursor represents the point (x,y) when T = 270 , the minimum value
assigned to T. The cos 270 = 0 and the sin 270 = −1 . In X1T you
(
)
(
)
entered 98.5cos ( T) and in Y1T you entered 98.5 sin ( T) + 110.5 . Do
the arithmetic. You will see that the coordinates of the minimum point of
the Ferris wheel should be (0,12), exactly what you see on your
screen.
Now press the right blue arrow once. You have told the calculator to move to the
next point which occurs when T = 275 . (Recall you set the Tstep at 5.)
Continue to press the right arrow until you have made a complete circle.
Modeling applications is one of the benefits of a graphing calculator. You may
want to read this explanation more than once.
Rodgers, K.
21
Chapter 3
Radian Measure
Section 3.1
Question 13 asks for the exact value of cos 225 . From the text, you know the
terminal side of this angle is in Quadrant III and the reference angle is 45°. Since the
cosine is negative in Quadrants II and III, you know your answer will be negative. You
should have also memorized the trigonometric functions for the basic angles. If so
2
2
you know that the cos 45 =
. Your answer is −
. Now use your calculator to
2
2
2
to a decimal and also to find cos 225 . Compare your answers. They
convert −
2
should be the same. Check your work with the calculator screen that follows.
( )
(
)
Question 41 asks you to find cos −315 . Your calculator should be in degree mode.
Alert! You must use the negative symbol and not the subtraction sign. Check your
screen with the following.
Question 49 asks you to find θ given sin θ = -0.3090 and θ in QIII . Use the following
sequence of keystrokes to complete this task. This question is directing you to find a
value for θ such that the sin θ = − 0.3090 .
press SIN-1
enter -0.3090
press ENTER
22
Chapter 3
TI-83
You have found an angle, but this is not the angle that your text asked you to find.
Your directions said to find θ such that 0 < θ < 360 with θ in the third quadrant, this
angle is in the fourth quadrant.
You have found a reference angle of 17.99897619, the absolute value of -17.99877619.
To find the value of the angle with terminal side in the third quadrant, add 180° to the
reference angle. The answer is 197.9989762. or 198.0 when rounded to the nearest
tenth.
Use this sequence of keystrokes to complete this question.
press
select
select
press
press
MATH
NUM from the menus across the top
abs
ENTER
ANS
By using the ANS key you do not have to retype your
answer from above. The calculator knows your last
answer.
enter +
enter 180
By adding 180 , you are placing the terminal side of the
angle in Quadrant III.
press ENTER
You should have gotten 197.9989762; this is your value for θ. Now check your answer
by finding the sin θ .
press SIN
press ANS
press ENTER
Check your screen.
Rodgers, K.
23
Chapter 3
TI-83
Interpret information on this screen. The original question asked you to find a value
for θ such that the sinθ = -0.3090. You found θ to be 197.9989762. Next you found
the sin(197.9989762) and when your calculator returned -.309, you knew you had
found the correct value for θ .
Question 59 directs you to find θ given the sec θ = 1.4325 with θ in QIV . Your
calculator does not have a SEC-1 key. However, from your previous study of
reciprocal identities you know the following:
1
sec θ
1
cos θ =
1.4325
 1 
θ = cos−1
 1.4325 
cos θ =
You would enter this in your calculator using the following keystrokes.
press COS−1
press (
enter 1/1.4325
press )
press ENTER
This angle is in the first quadrant and the question asks for an angle in the fourth
quadrant. The correct answer is found be subtracting 45.7 from 360 . Use the ANS
key on your calculator to find the correct angle. Since your answer is positive, it is not
necessary to take the absolute value before performing the addition or subtraction.
Finally, check your answer by finding the secant of this angle. If you are correct, your
answer will be 1.4325.
24
Chapter 3
TI-83
Section 3.2
Question 7 asks you to find the radian measure of angle θ , if θ is a central angle of
a circle with radius of 14 cm and an intercepted arc length of 12 cm. Recall that
s
θ (in radians) = .
To enter this on the Home Screen of your calculator, use
r
parentheses around each fraction. Check your calculator screen with the screen that
follows.
Interpret your answer. The measure of angle θ is 2 radians.
Question 11 asks you to give the reference angle in both degrees and radians. The
reference angle for 30 is 30 . To find the reference angle in radians, you must
convert 30 to radians. Your paper-pencil work should resemble the following:
 π  π
30 ∗ 
=
180  6
Note. If you need an exact numerical answer, you must use the previous method.
Your calculator will only give you a decimal approximation.
The following keystrokes convert an angle from degree measure to radian measure.
press
select
press
press
enter
press
select
MODE
Radian
ENTER
CLEAR
30
ANGLE
#1 for degree
Use the blue arrows to move the cursor to Radian.
Pressing either ENTER or 1 will paste the
degree symbol on the Home Screen.
press ENTER
Rodgers, K.
25
Chapter 3
TI-83
Interpret your answer. 30 is approximately 0.5235 radians. Compare this
answer with the exact numerical answer you obtained.
Use your calculator to
compare your two answers.
enter
press
enter
press
π
÷
6
ENTER
To complete Question 23, you must be able to convert 120 40' to radians.
enter
press
select
enter
press
select
press
120
ANGLE
degree
40
ANGLE
minute
ENTER
Your calculator has converted 120 40' to decimal degrees; it has not converted the
answer to radians.
press ANS
press ANGLE
select degree
press ENTER
You must tell the calculator that you are entering an angle
that is in degree measure.
Since you are in Radian mode, the calculator now
converts the measure of this angle to radians.
Note. You could do all of this in one step by entering (120 40′ ) in your calculator.
Now interpret your answer. 120 40' is approximately 2.11 radians. (You can
have your calculator round to hundredths; however, it is probably easier for you to do
this mentally.)
26
Chapter 3
TI-83
Question 43 asks you to convert an angle with a measure of one radian to degrees.
(You know the 1 represents radian measure; if the 1 represented degree measure,
then the degree symbol would have followed the 1.)
Note. If you want to convert to degree measure, then set your calculator to degree
mode.
press
select
press
press
enter
press
select
press
MODE
degree
ENTER
CLEAR
1
ANGLE
radian (#3)
ENTER
Either press 3 or ENTER.
After you have completed question 51, you can use your calculator to check your
answer. From previous work, you know
4π
3
∧
π
θ = and θ in QIII
3
θ=
∧
θ is the symbol for reference angle.
3
π
and sin   =
.
2
3
Since the sine is negative in the third quadrant, you must take the negative of your
answer.
3
 4π 
sin
=−
 3 
2
Rodgers, K.
27
Chapter 3
TI-83
On your calculator:
press SIN
enter (4π÷3)
press ENTER
The key for π is below the CLEAR key.
Compare your calculator answer with your exact numerical answer.
Alert! Always check the mode setting of your calculator. If you had not been in
radian mode, you would have still gotten an answer, a wrong answer.
π π 3π
Question 73 asks you to find the y--value given y = sin x, for x = 0, , , , π .
4 2 4
Certainly you could find this problem one value at a time. For example, after you have
checked to make sure your calculator is in radian mode, use the following keystrokes.
press SIN
enter 0
press ENTER
Interpret your answer. Y is zero when x is zero giving the ordered pair (0,0). To
complete the problem, you would need to continue this process for each x-value.
A second method is to enter all of the x-values at one time. Try the following key
strokes.
press SIN
press {
π π 3π
enter 0, , , , π
4 2 4
enter })
press ENTER
The bracket tells the calculator you are going to
enter a list.
28
Chapter 3
TI-83
Note. The three dots to the right tell you there are more answers. Use the right
arrow key and scroll to the right to see the rest of the answers. To get fewer
decimal places go to MODE and change the decimal setting. The following
screen gives the answers rounded to hundredths.
A third procedure for answering this question is to use the Table Feature. Try the
following keystrokes.
press
enter
press
enter
enter
press
Y=
sin x
TBLSET
0 in TblStart
π/4 in ∆Tbl
TABLE
Interpret your answer. You have the following ordered pairs. You know the x-values
π π
are 0, , ,etc. because you told the calculator to start the x-values at 0 and to
4 2
π
increase each x-value by . You have the following ordered pairs: (0,0),
4
π
 π   3π
( ,.70711),  ,1 ,  ,.70711 , etc.
4
2
4
Note. You can conveniently use the Table Feature when the independent variable is
increasing by the same quantity. In the preceding example, the independent
Rodgers, K.
29
Chapter 3
TI-83
π
. All three procedures are suitable methods; learn to
4
use the method best suited for the question you are investigating.
variable was increasing by
Section 3.3
Question 1 asks you to find the values of all six trigonometric functions given the
angle measure of 150 . Without a doubt, you should memorize the trigonometric
functions for the basic angles. You know 150° is in the second quadrant and the
reference angle is 30° (180 − 150 ) . If you have memorized the sine and the cosine
for 30 , you can now find the values for all six trigonometric functions.
To use the unit circle to answer this question, use the following keystrokes.
press MODE
select Par
press ENTER
select Degree
press ENTER
press Y =
select X1T and enter cos(T)
select Y1T and enter sin(T)
press TBLSET
enter 0 in TblStart
enter 10 in ∆ Tbl
press TABLE
You need to be in parametric mode.
Interpret the table. When T (the angle measure) is 0, the cos(0) = 1 and the
sin (0) = 0. Skip down to 30--the information from this table tells you that the cos(30)
= 0.86603 and the sin (30) = 0.5. By scrolling down the table, you can read the sine
and cosine for every angle that is a multiple of 10.
press WINDOW
enter the following
30
Chapter 3
TI-83
Tmin = 0
Tmax = 360
Choose 360 because there are 360 in a circle.
Tstep = 10
Choose 10 because 10 was used in the table.
press ZOOM
select Zsquare
press ENTER
You could have also pressed 5 to make the same
selection.
press TRACE
You have a picture of the unit circle. Notice the values displayed on the bottom of
your screen. When the angle (T) is zero, then the x-value which you defined as the
cos (T) is 1 and the y-value which you defined as sin (T) is 0.
Press the right blue arrow. You can read the values for the cos (T) and sin (T) for
every multiple of 10 angle on the unit circle. Try it.
Suppose you want to know the x and y-values when T = 12. As you trace around the
circle, the T-values are multiples of 10. To find the x and y-values when T is 12, just
press 12 and your calculator will return the correct x and y-values. (You must have
first pressed TRACE for this to work. If you press 12 without first pressing TRACE,
your calculator will return you to the Home Screen.)
You could also use the following keystrokes to find the cosine and sine when T = 12.
press
select
press
enter
press
CALC
value
ENTER
12
ENTER
Check your screens with the screens that follow.
Rodgers, K.
31
Chapter 3
TI-83
By knowing this series of keystrokes, you can enter any value for T.
Note. If you want your answer in radians, then repeat the preceding process. First
put your calculator in radian mode; change the window setting to the following
Tmin = 0
Tmax = 2π
Tstep =
Choose 2π because there are 2π radians in a circle.
π
π
12
12
press GRAPH
is a convenient Tstep because it will include all of the basic angles.
(You will see the same unit circle; however when you
TRACE, the angles measure (T-values) will be in radians
and not degrees.
After you have completed your drawing for question 51 use your calculator to show
that sin 180 − θ = sin(θ ).
(
press
enter
enter
press
enter
enter
press
)
Y=
Y1 = sin(180 - X)
Y 2 sin(X)
TBLSET
any number in TblStart
any number in ∆Tbl
TABLE
Look at your values in the columns Y1 and Y2 . The numerical values are the same in
both columns. These are numerical values for the identity that you were showing true
in question 51.
32
Chapter 4
Graphing and Inverse Functions
Section 4.1
Section 4.1 of your text introduces the graph of the sine function. First
you look at ordered pairs (x,y) that make y = sin x a true statement.
Secondly, you obtained the graph of the sine function by using the unit
circle definition. The following sequence of keystrokes will graph the unit
circle and the sine function.
press
select
press
select
press
select
Mode
Radian
ENTER
Par
ENTER
Simul
press
press
press
enter
enter
enter
enter
press
enter
enter
ENTER
CLEAR
Y=
cos (T) in X1T
sin (T) in Y1T
T in X2 T
sin (T) in Y2 T
WINDOW
0 for Tmin
2π for Tmax
π
for Tstep
12
-2π for Xmin
2π for Xmax
π
for Xscl
2
-4 for Ymin
4 for Ymax
1 for Yscl
enter
enter
enter
enter
enter
enter
enter
Simul (simultaneous) tells the calculator to
graph the entries simultaneously rather
than sequentially.
35
Chapter 4
TI-83
Note. Instead of manually setting the window, you could have pressed ZOOM and
selected Ztrig; however, when you are first learning to graph trigonometric
functions, manually entering the window values enhances your
understanding of the processes.
The real value of this model comes when you start to TRACE around the circle and
move from one graph to the other. Press TRACE.
Notice the expressions on the top of the screen; this tells you that you are tracing on
the graph defined by these two equations. At the point where the cursor is flashing
the angle (T) is zero, the cos (T) is one and the sin (T) is 0. Press the down arrow.
Notice that the expressions at the top of the screen have changed. You are now
tracing on the graph defined by the second set of equations. The cursor moved to the
point (0,0). Interpret this. Remember, you are graphing y = sin (X). You defined the
x-value to be equal to the angle value which is T.
For this particular case, the
values for X and T are equal because you defined them as such. The y-value is the
sin (T).
Press the right arrow six times. (You set the T-step to
π
; if you press the arrow six
12
π
π
times you have found 6i or .) Check your knowledge against what the calculator
12
2
π
π
is telling you. You know the sin  = 1 and
≈ 1.5707963. Now look at the
2
2
π
calculator. Your graph shows that when x = , y = 1. Press the down arrow. The
2
Rodgers, K.
34
Chapter 4
TI-83
cursor has moved back to the unit circle; however, the sine value did not change. The
x-value changed because you defined the x-value for the first graph to be
cos (T). Continue to trace around the unit circle.
Now look at the cosine function. Leave the parametric equations for the unit circle in
place but make the following changes to graph the cosine function.
leave
enter
press
press
T in X2 T
cos (T) in Y2 T
GRAPH
TRACE
Spend some time interpreting what you see on the calculator screen. When
the angle (T) is zero you see that the cos (T) = 1 and the sin (T) is 0. Press the down
arrow.
The cursor has moved to the second graph. Again, the X and T values are
equal. Remember you defined them that way. Notice now that the y-value is one.
You defined the y-value to equal the cos (T) and the cos (0) = 1. Use the blue arrow
keys to continue exploring the relationship between these two graphs.
To answer question 1, first generate a table of values. Your table of values should
resemble the following table.
35
Chapter 4
TI-83
x
decimal app
y
decimal app
0
0
1
1
π
4
π
2
3π
4
0.785
2
2
0.707
1.571
0
0
π
3.142
5π
4
3π
2
7π
4
2π
2.356
3.927
−
2
2
−0.707
−1
−
2
2
−1
−0.707
4.712
0
0
5.497
2
2
0.707
6.283
1
1
Use the following sequence of keystrokes to generate this table.
press MODE
select Radian
press ENTER
select Func
press ENTER
press CLEAR
press Y =
enter COS (X) in Y1
press TBLSET
enter 0 in TblStart
π
enter
∆Tbl
4
press TABLE
You should always check to see whether your
calculator is in degree or radian mode.
You need to return to function graphing.
π
, since the directions said to use x4
π
values that are multiples of .
4
You select
Compare this table with the table you generated without the calculator.
Rodgers, K.
36
Chapter 4
TI-83
Note. One feature of the calculator-generated table is the ability to scroll up and
down the table. By using the blue arrow keys you can see an infinite number
of values. Try it!
Question 1 also asks you to sketch the graph of y = cos x from the table of values.
Compare your paper-pencil graph with a calculator-generated graph.
press
enter
press
enter
enter
enter
enter
enter
enter
press
Y=
COS (X) in Y1
WINDOW
-2π for Xmin
2π for Xmax
π
for Xscl
4
-4 for Ymin
4 for Ymax
1 for Yscl
GRAPH
Press TRACE.
Compare the (x,y)-values to the corresponding (x,y)-values of your table; they should
be the same. Do you want to check a second value in your table with the graph?
π
How about letting x = ? Use the following keystrokes.
4
press TRACE
π
enter
for X
4
press ENTER
37
Chapter 4
TI-83
Take a moment to relate what you see on the screen to your previous paperpencil work. You see the cursor flashing on a point on the graph and the coordinates
of the point are shown at the bottom of the screen. Compare these values with values
in your table. If you were asked to give the domain of the function, you would answer
all real numbers; however, you can see very clearly that the range values are from -1
to 1.
Before leaving this question, learn one more feature of the calculator.
press MODE
select Radian
press ENTER
select G-T
press ENTER
press GRAPH
press TRACE
(G-T stands for graph and table.)
Interpret the screen! You have the graph of the cosine function on the left and the
table of values on the right. Notice that the cursor is flashing on the point at the left
and the coordinates of this point are at the bottom of the screen as well as highlighted
in the table. If you wish to scroll down the table, press TABLE and use the blue
arrows. If you wish to move the cursor around on the graph, press TRACE and use
the blue arrows.
If you wish to have your calculator generate a table for question 3, you will have to
recall the reciprocal identities from Chapter 1. The calculator does not have a CSC
1
key for cosecant. You are asked to find y = csc x ; however, csc x =
. Hence
sinx
1
in your calculator to find y = csc x . Use the same table settings and
enter y =
sin x
window settings as you used for question 1.
To compete question 5, you must interpret what you see on the calculator screen.
Rodgers, K.
38
Chapter 4
TI-83
press MODE
select Radian
press ENTER
press Full
press ENTER
press CLEAR
press Y =
enter TAN (x)
press WINDOW
enter -2π for Xmin
enter 2π for Xmax
π
for Xscl
enter
2
enter -6 for Ymin
enter 6 for Ymax
enter 1 for Yscl
Is this the graph of y = tan (x)? Are the straight lines a part of this graph? The answer
is no. As long as your graph is in connect mode the calculator will connect two points
sin(x )
and whenever the
that are close together. Analytically you know that tan(x ) =
cos(x )
cos(x ) = 0, the tangent function is undefined. Hence for all x-values of the form
(k ) π , where k is an integer , the cos(x) = 0 and the tangent function is undefined.
2
One way to check this graph, or any graph with what appears to be vertical lines, is to
change the calculator form connect mode to dot mode.
press
select
press
press
MODE
DOT
ENTER
GRAPH
The straight lines have disappeared; the lines are not a part of the graph of y = tan (x).
39
Chapter 4
TI-83
Note. DOT mode is very useful; however, you should normally leave your calculator
in CONNECTED mode. DOT mode gives the appearance that
within
each
interval the graph is not continuous. That is not true, the
graph is continuous
within the interval; as the graph is stretched out, there
simply is not a sufficient
number of pixels on the screen to give the
appearance of a connected graph.
Before answering question 13, use the following keystrokes to visualize when the
cos ( x ) = 0 .
Note. Since you have been using many features of the calculator check the MODE
prior to working this problem. For this investigation, all of the selections on the
left should be black.
press Y =
enter cos x in Y1
press WINDOW
You should start to have a feel for setting the window of your calculator. You want to
view the graph from 0 to 2π since the period for the cosine function is 2π. This tells
you your X settings must include an interval of this length. You could select 0 for the
minimum x-value and 2π as the maximum x-value. Sometimes it is helpful if you can
π
view the graph from the left and right of the interval. Maybe - for the minimum
4
9π
for the maximum value would be better. That is a decision that you
value and
4
must make. You should recognize that the amplitude for y = cos x is 1 and hence the
range is [-1,1]. You could use those exact settings for the minimum and maximum
values for y. Again, it is probably better to see above and below the actual graph.
Maybe -4 for the minimum y-value and 4 for the maximum y-value would be a better
π
π
or . You could press ZOOM and
selection. A good choice for the Xscl is either
4
2
select ZTRIG; however, unless you understand the window settings, you could
misinterpret the graph. Always be hesitant to use calculator magic; that is just
pushing a button and viewing the results.
Rodgers, K.
40
Chapter 4
TI-83
Before you just start to TRACE, have a look at the values in the TABLE. Go to
π
π
TBLSET and enter zero as the starting point and
for ∆Tbl. (
was chosen
12
12
because 12 is the common denominator for all of the basic angle measures of
π π π
π
, , and .) Now press TABLE. Compare your calculator screen with the screen
6 4 3
2
that follows.
You are looking for x-values where the Y1 = 0 . When x ≈ 1.5708, then Y1 =0 . You
could find other such values by using the blue up and down arrow keys.
press GRAPH
press CALC
select zero
The calculator is asking you for an x-value to the
left of the zero. (Use the left blue arrow until the
cursor is flashing to the left of the zero.) You will
see a above the graph. You are defining an
interval in which the calculator will find the zero (xintercept) in question.
press ENTER
Now the calculator is asking you for an x-value to
the right of the curve. Use the right blue arrow until
the flashing cursor is to the right of the zero.
press ENTER
The calculator now asks you to GUESS. Simply
trace until you are close to the point of zero.
press ENTER
41
Chapter 4
TI-83
Interpret what you see on the screen. At the point where the cursor is flashing is a
zero of the function in the defined interval, and the coordinates of that point are
(1.570796, 0).
Repeat this process to find the second zero.
Before you begin your paper-pencil work do one last thing. Expand the window.
press WINDOW
enter -4π for Xmin
enter 4π for Xmax
π
enter
for Xscl
2
enter -4 for Ymin
enter 4 for Ymax
enter 1 for Yscl
Do you recognize that the zeros are occurring at regular intervals? Now complete
your paper-pencil work and compare your answers with the zeros from this graph of
the function. After all when you are solving cos ( x ) = 0 , you are searching for x-values
such that when you find the cosine of that x-value the answer is zero. This
corresponds to the x-intercepts on the graph of the function.
Problem Set 4.2
Use your graphing calculator to discover the meaning of amplitude and how it affects
the graph of the function.
Rodgers, K.
42
Chapter 4
TI-83
press MODE
select Radian
press ENTER
press Y =
enter cos x in Y1
enter 2 cos(x ) in Y2
enter 5 cos(x ) in Y3
press WINDOW
enter -2π for Xmin
enter 2π for Xmax
π
enter
for Xscl
2
enter -6 for Ymin
enter 6 for Ymax
enter 1 for Yscl
Remember
the
calculator,
in
sequential
mode,
graphs
in
order-Y1 first, Y2 second, etc. This helps you associate the graph with the correct function.
However, if it is still difficult for you to know which graph to associate with which
function, there are two things that you can do.
press Y =
Use the blue arrows until the cursor is flashing on the \ to the left of Y2 .
press ENTER
Did the \ become a bold line?
Use the blue arrows until the cursor is flashing on the \ in Y3 .
Continue pressing ENTER until you see a dotted line.
This is one method for distinguishing between the graphs.
keystrokes for a second method.
Use the following
43
Chapter 4
TI-83
press Y =
Use the blue arrows to change all of the \ back to the normal line.
press MODE
select Radian
press ENTER
select HORIZ
This provides a split screen--you can view the
graph as well as the functions that you have
entered.
press ENTER
press Y =
press TRACE
Use the up and down blue arrow keys and note the change in the y-values. The xvalue stays the same.
press Y =
edit Y2 to 4 cos(x ) and Y3 to 8 cos(x )
press GRAPH
Does your screen resemble the screen that follows?
You do not have a complete graph. This means you need to change the settings in
the WINDOW. It appears that the y-values need to be changed.
press WINDOW
Rodgers, K.
The x-values were OK; just change the y-values.
44
Chapter 4
TI-83
Note. With the split screen you will have to use the blue arrow keys to scroll
down to the y-values.
enter -10 for Ymin
-10 was selected for the minimum y-value,
but you could have selected -11, or -12, etc.
enter 10 for Ymax
enter 1 for Yscl
press GRAPH
Press TRACE and use the down arrow keys as you did previously.
Try one more thing.
press
select
press
press
MODE
G-T
ENTER
GRAPH
press TRACE
Use the up and down blue arrows to change between the graphs of the functions.
Your screens should look like the following. In each case note that the x-value does
not change, but the y-value does.
Can you see that the general shape of the graphs does not change. The graph has
been stretched vertically by a factor equal to the amplitude. From Section 4.1, the
definition of amplitude is:
45
Chapter 4
TI-83
The greatest value of y is M and the least value of y is m, then the
1
amplitude of the graph of y is defined to be A = M - m .
2
From Section 4.2, the definition is generalized to say:
If A is a positive number, then the graphs of y = A sin x and y = A cos x will
have amplitude |A|.
Now use your graphing calculator to discover the meaning of period and how it affects
the graph of the function.
press
select
press
select
press
press
enter
enter
enter
press
enter
enter
enter
enter
enter
enter
MODE
Radian
ENTER
Full
ENTER
Y=
cos(x ) in Y1
cos(2x ) in Y2
cos(4x ) in Y3
WINDOW
-2π for Xmin
2π for Xmax
π
for Xscl
2
-2 for Ymin
2 for Ymax
1 for Yscl
Does your graph resemble a broken tape cassette?
There are several things that you can do to make the graph easier to interpret. Press
Y = and turn off Y3 . You do this by using the down error until the cursor is flashing on
cos (4x) and then use the left arrow until the cursor is flashing on the equal sign. Now
press ENTER. Did the equal sign change colors? (When you want to turn this graph
back on, move the cursor until it is flashing on the equal sign and press ENTER.)
Rodgers, K.
46
Chapter 4
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Now move your cursor up to cos (4x) and to the left until the cursor is flashing on the
symbol to the left of Y2 and press ENTER. (You should see the symbol change from
a narrow line to a heavy line.) Finally press WINDOW and change the minimum value
for X to 0. Press GRAPH.
Study the graph. Look at the screens below. On the first screen is the graph of y =
cos x and on the second screen is the graph of y = cos (2x). The interval is 0 to 2π on
both screens.
The screen on the left shows one complete cycle of the cosine curve while the
screen on the right shows two complete cycles of the cosine curve. To make room for
the curve twice, the curve had to be compressed. The length of the period in the
graph on the left is 2π. The length of the period for the graph on the right is π.
Now compare the graphs of y = cos (x) and y = cos (4x).
y = cos (x)
y = cos (4x)
Can you see that the graph on the right is actually four repetitions of the graph
on the left. The length of the period of y = cos (x) is 2π and the length of the period
π
π

= 2π ÷ 4 
on the right is .

2
2

Now compare the graphs of y = cos (x) and y = cos ( 12 x) displayed on the
following screens.
y = cos (x)
y = cos ( 12 x)
47
Chapter 4
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Can you see that the graph on the right is only half of the graph on the left?
You would have to extend the maximum x-value to 4π to see a complete period. The
length of the period for y = cos (x) is 2π and the length of the period for
y = cos ( 12 x) is 4π. ( 2π ÷ 12 ) Compare these examples with the definition of period in
your text.
For any function y = ƒ(x), the smallest positive number p for which ƒ(x + p) = ƒ(x) for all
x is called the period of ƒ(x).
If B is a positive number, the graphs of Y = A sin (Bx) and y = A cos (Bx) will each have
2π
a period of
.
B
Question 1 asks you to graph one complete cycle of y = sin (2x). Before you start to
enter this in your calculator, look at the function analytically and answer the following
questions. What is the period of y = sin (2x)? The coefficient of x is two--the B value
2π
2π
is two. You also know that the period is
. The period of y = sin (2x) is
or π .
B
2
The amplitude is 1. Now enter y = sin 2 x this in your calculator and verify your
analytical calculations. Check your calculator screens with the screens that follow.
Note. As you sketch a graph on your paper, be sure to label all of the x and yintercepts.
Question 9 asks you to graph one complete cycle of y = csc (3x ) .
csc(3x ) =
Rodgers, K.
1
sin(3x )
48
Chapter 4
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Since the cosecant is the reciprocal of the sine function, you know that whenever the
sine function is equal to zero, the cosecant function is undefined. The sine function is
equal to zero at kπ where k is an integer. You also know that the period of the
cosecant function is equal to the period of the sine function; the cosecant function
does not have amplitude.
Before you start to graph y = csc (3x ) , determine the period.
period =
2π
3
(Remember that
2π
gives the period.)
B
When 3x equals kπ (k is an integer), the cosecant function will be undefined. In other
kπ
(k is an integer), there will be a vertical asymptote. Now enter
words when x =
3
the function in your calculator.
press MODE
select Radian
press ENTER
press Y =
1
enter
sin(3x )
press WINDOW
enter 0 for Xmin
2π
enter
for Xmax
3
π
enter
for Xscl
3
enter -5 for Ymin
π
was
3
chosen since the vertical asymptotes will occur at
π
multiples of .
3
Select y-values for the minimum and the
maximum that permits you to see the shape of the
graph.
There is no best value for this x-scale;
enter 5 for Ymax
enter 1 for Yscl
press GRAPH
49
Chapter 4
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Is the straight line part of the graph? If you do not know the answer, use the following
keystrokes.
press
select
press
press
MODE
Dot
ENTER
GRAPH
The answer to the preceding question was no, the line that appear to be
vertical is not part of the graph.
ALERT! Look at the preceding graph. It is not a totally accurate graph of
A more
y = csc (3x ) . The graph of this function has a range of ( −∞, −1] ∪ [1, ∞ ) .
accurate graph of this function is one that you have manually enhanced to indicate
that the graph approaches positive infinity as the x-values approach the asymptotes.
The reference curve for this graph is y = sin(3x ) . Enter this function in your calculator
and look at the graph.
Rodgers, K.
50
Chapter 4
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Note. Every time the sin(3x) = 0, the csc3x is undefined. This supports your earlier
1
and when the sin(3x) = 0, you have
work. You know that the csc(3x ) =
sin(3x )
a zero in the denominator causing the function to be undefined. Also note that
the two functions are equal at the relative maximum and minimum points of
y = sin(3x).
Look at question 23. Use your paper-pencil skills to determine the period and the
amplitude before you start to graph. This information tells you how to set your
WINDOW. By inspection, you know the amplitude is 12 . Your paper-pencil work to
find the period should resemble the following.
2π
π
2
2π 2
i
p e rio d =
1 π
p e rio d = 4
p e rio d =
Use the following strokes to graph the function.
press Y =
1 π 
sin  x 
enter
2 2 
press WINDOW
enter 0 for Xmin
enter 4 for Xmax
enter
enter
enter
enter
press
π
for Xscl
2
-2 for Ymin
2 for Ymax
1 for Yscl
GRAPH
If you want to see only one period of the graph set
the x-values from 0 to 4. If you want to see more
than one period or if you want to see to the left and
right of the graph then expand the x-values for the window.
Finding the length of the period helps you determine the
window settings.
51
Chapter 4
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Interpret the graph. You know you have the general shape of the sine curve; you
know the amplitude is 12 and the period is 4; the graph supports your analytical
calculations. Also note that the graph intersects the x-axis at the midpoint of the
period. You will find this always to be true if there has not been a vertical shifting or a
rotation of the graph.
Before graphing one period of question 29, find the period and the vertical
asymptotes. Your preliminary paper-pencil work should be as follows.
y = 2 tan ( 3x )
π
B
π
period =
3
period =
1 π
π
vertical asymptotes = ± i + k, where k is an integer
2 3
3
π
3π
5π
examples of vertical asymptotes are x = , x = , x =
6
6
6
Note. The tangent function does not have amplitude. The graph of this function is
stretched by a factor of 2 when compared to the graph of y= tan ( 3x ) .
Now you are ready to enter this function in your calculator.
press
select
press
press
enter
press
MODE
Radian
ENTER
Y=
2 tan(3x ) in Y1
WINDOW
π
enter
for Xmin
6
The directions for this problem say to graph one
π π
period of the function hence the interval  ,  or
6 2
Rodgers, K.
52
Chapter 4
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π
would be ok. Notice
3
that the endpoints are not included.
any other period of length
π
for Xmax
2
π
enter
for Xscl
6
enter
enter -5 for Ymin
π
was
6
chosen since the vertical asymptotes will occur at
π
multiples of .
6
Select y-values for the minimum and the
maximum that permits you to see the shape of the
graph.
There is no best value for this x-scale;
enter 5 for Ymax
enter 1 for Yscl
press GRAPH
Expand the x-values so as to include more than one period of the graph.
Alert. What appears to be vertical lines are not vertical asymptotes and are not part
of the graph of y = 2 tan ( 3x ) . You can always check to see if the lines are part
of the graph by going to Dot Mode.
Use your calculator to investigate the graph.
press TRACE
π
enter
6
press ENTER
53
Chapter 4
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Interpret the screen. When you asked the calculator to find the y-value for x =
π
, the calculator returned y =. This is the calculator’s way of saying “the function is
6
π
undefined at x = ”. This supports your earlier work. You had found a vertical
6
π
asymptote at x = . (Recall vertical asymptotes occur at x-values where the tangent
6
π
π
function is undefined.) If
is one vertical asymptote and the period is , the next
6
3
3π 
π
vertical asymptote should occur at
which simplifies to  . Try it. Press TRACE
6 
2
π
and enter . Is there a y-value?
2
You have supported your paper-pencil work with the graph. You can easily
translate the graph on your calculator screen to paper because you know that each
π
π
unit on the x-axis is equal to
. (You know this because you set the x-scale at .)
6
6
Question 33 asks you to graph one complete cycle of y = 4 + 4 sin(2x ) . Again, look at
the problem analytically before starting to graph. Given y = C + A sin(Bx ), the C tells
2π
you the amount of the vertical shift, the |A| gives the amplitude, and
gives the
B
period. Hence the graph of y = 4 + 4 sin(2x ) has a vertical shift up of 4 units, an
amplitude of 4, and a period of π. You are now ready to enter this function in your
calculator.
press
select
press
press
enter
press
enter
MODE
Radian
ENTER
Y=
4 + 4 sin(2x )
WINDOW
0 for Xmin
Since the period is π , you could set the window
from 0 to π. You would then see exactly one
period.
enter π for Xmax
Rodgers, K.
54
Chapter 4
π
for Xscl
4
enter -2 for Ymin
TI-83
enter
When deciding how to set the y-values, recall that
you have an amplitude of 4. That would mean the
graph would have a minimum y-value of -4 and a
maximum y-value of 4; however, you also had a
vertical shift up of 4 units. You should then add 4
to both the minimum and maximum y-values. If
you used 0 and 8 for your minimum and maximum
values, you would have no space above or below
the graph. Usually this is not good. Maybe -2 and
10, would be better y-values. Do not think that
these are the only acceptable values; a -5 and 13
would work just as well as would numerous other
y-values.
enter 10 for Ymax
enter 1 for Yscl
press GRAPH
Interpret the graph. Do you have a complete cycle? Does the amplitude and vertical
shift support your earlier calculations? In this case the answer is yes, if the answer
had been no, then you should have checked both your analytical work and your
calculator keystrokes.
Continue your exploration of the sine and cosine functions by completing the
following keystrokes.
press Y =
enter sin(x ) in Y1
π

enter sin x +  in Y2
2
Use the blue right arrow to move the cursor until it
is flashing on the symbol to the left of Y2 . Press
ENTER until the heavy line is flashing. This will let
you easily distinguish between the graphs of the
two functions.
enter -2π for Xmin
enter 2π for Xmax
55
Chapter 4
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π
for Xscl
2
enter -2 for Ymin
enter 2 for Ymax
enter 1 for Yscl
press GRAPH
enter
π

Interpret the graph. The heavy line which represents y = sin x +  is to the left of
2
π
units. Look at another example.
y = sin(x ). There has been a horizontal shift left of
2
π

Let y = sin x +  .
3
press Y =
enter sin(x ) in Y1
π

enter sin x +  in Y2
3
press GRAPH
π

In relation to the graph of y = sin(x )the graph of y = sin x +  has been shifted to the
3
π
left units. Notice the graph has not moved vertically. You should now repeat the
3
previous examples using the cosine function.
Section 4.3
π

Question 1 asks you to graph y = sin x +  . Before you begin to enter this in your
4
calculator compare the equation to the generalized form y = Asin(Bx + C). You know
that in question 1, the value for A is one, the value for B is one, and the value for C is
Rodgers, K.
56
Chapter 4
TI-83
π
. From this you know the amplitude is one, the period is 2 π , and the phase shift is
4
π
units to the left.
4
press
select
press
press
enter
MODE
Radian
ENTER
y=
sin ( x ) in Y1
π

enter sin x +  in Y2
4
press WINDOW
π
enter - for Xmin
4
enter 2π for Xmax
enter
π
for Xscl
4
enter -2 for Ymin
Make this curve darker.
π
units.
4
That is an appropriate choice for the minimum xvalue. Normally you would select zero for the
minimum x-value; however the graph has
π
been shifted to the left
units. Hence you
4
π
subtract
from zero.
4
π
Add the length of the period, 2π, to initial value, - .
4
π
There is no best value for this x-scale;
was chosen
4
π
since the phase shift was to the left
units.
4
Select y-values for the minimum and the
maximum that permit you to see the shape of the
graph.
The phase shift is to the left
enter 2 for Ymax
enter 1 for Yscl
press GRAPH
57
Chapter 4
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Interpret the graph. Do you see one complete cycle of the function? Is the amplitude
π
units? The answer to all of the questions is
one? Is there a phase shift to the left
4
yes. (Actually you see more than one complete cycle since you have expanded the
window to include the phase shift.) The graph supports your analytical work.
Question 11 asks you to identify the amplitude, period, and phase shift of
 
π
y = sin(2x − π) and to sketch the graph. First write the function as y = sin 2 x −   .

2 
 2π 
Now you know the amplitude is one; the period is π since   = π. , and the phase
 2 
π
shift is
units to the right. Now enter y = sin(2x − π) in your calculator using the
2
keystrokes listed previously. Before you press GRAPH, set the WINDOW. The
π
units to the right; make this the minimum x-value. The period is π, so
phase shift is
2
3π
make the maximum x-value equal to
. (Recall to find the ending point of this
2
period, you should add the length of the period to the beginning value.)
Now interpret the graph. Make sure the graph supports your analytical work. If you
find it difficult to interpret the graph without seeing the y-axis, change the minimum xπ

value to 0 and change the y = screen to the following. Y1 = sin ( 2 x − π )  ≤ x  . (The
2

π
π

 2 ≤ x is telling the calculator to start at 2 .)
To verify your paper-pencil work, do the following to find the coordinate of the
x-value for the beginning of the period.
press Trace
Rodgers, K.
58
Chapter 4
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π
,
2
calculator had sufficient power this
keystrokes.
Note. The Y = 4.102E − 10 is scientific notation and is 0.0000004102. When x =
the y-value should be zero and if the
would be the case. Try the following
press CALC
select value
π
enter
for the x-value
2
press ENTER
π
for your minimum x-value in the
2
window setting the calculator had entered a decimal representation for this value, a
π
value when rounded off that was slightly larger than . The error message is telling
2
you that the x-value you requested is not in the interval. No problem.
Did you get an error message? If you had entered
press WINDOW
enter 0 for Xmin
press CALC
select value
π
enter
2
The graph was shifted
π
units to the right. Continue to trace along the function.
2
The period is π; if this is correct the ending point of the cycle that began at
π
should
2
π
+ π ≈ 4.712. You will have to change the maximum x-value to a larger value--2π
2
for example.
be
59
Chapter 4
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Your graph supports that the period is π and further investigation will support that the
amplitude is one.
To get a better picture of the graph, you could have done the following.
press GRAPH
π
Again, when you entered the  ≤ x  , you were limiting the permissible x-values to
2
π
values greater than or equal to .
2
press TRACE
π
enter
2
This screen supports your work that the period begins at
representation for
π
is approximately 1.571.)
2
π
. (Recall the decimal
2
π
π
3π

Question 33 asks you to graph y = 4cos 2x −  , − ≤ x ≤
and to label the axes
2
4
2
so that the amplitude, period, and phase shift are easy to read.
Rodgers, K.
60
Chapter 4
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Before entering this function in your calculator, look at the question analytically. First
write the problem in the form y = Acos(B(x + C)). You do this by factoring.
 
π 
y = 4 cos 2 x − 

4 
π

(Mentally multiply 2 x −  ; did you get the original
4
π

expression of cos 2x −  ?
2
Once you have rewritten the function, you know the value of A is one, the value of B
π
is two, and the value of C is − . Hence the amplitude is 4; the period is π, and the
4
π
phase shift is
units to the right. Now you are ready to use your calculator. As
4
always, check to be sure you are in radian mode.
press y =
 
π
enter 4 cos 2x −   in Y1

2 
Enter the function as written in your text. If you
have made an arithmetic error in your paper-pencil
work, you do not want to graph your error.
press WINDOW
π
enter - for Xmin
4
The directions give the interval −
enter -
3π
for Xmax
2
π
enter
for Xscl
4
π
for the minimum x-value.
4
π
3π
≤x ≤
, so
4
2
enter
There is no best value for this x-scale;
π
was chosen
4
π
units.
4
Since the amplitude is 4, you need a
number smaller than -4.
since the phase shift was to the left
enter -5 for Ymin
enter 5 for Ymax
enter 1 for Yscl
press GRAPH
61
Chapter 4
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On the right is the graph of y = cos(x ). Use this to interpret your graph of
 
π 
y = 4 cos 2 x −  on the left. The function has amplitude of 4; the graph supports

4 
that. The function has a period of π; the graph shows one complete cycle from
π
π
5π
to
. The phase shift is
units to the right; look at the graph on the right and
4
4
4
note that the cycle begins at 0; now look at the graph on the left; one cycle begins at
π
π
, a shift of
units to the right. Your graph supports your analytical work.
4
4
π

Question 41 asks you to graph y = csc  x +  by first graphing the reference curve.
4
The reference curve for the cosecant function is the sine curve. First analyze the
π

function y = sin x +  . From your previous work, you know that the amplitude is
4
π
one, the period is 2π, and the phase shift is
units to the left. Recall that the sine
4
function and the cosecant function are inverse functions. From this you know
1
π
π


csc  x +  =
; hence when the sin x +  = 0 , the function is undefined.
π

4
4
sin x + 


4
π
π


Before graphing y = csc  x +  , graph the reference curve y = sin x +  .
4
4
press y =
 π
enter sin  x+  in Y1
 4
press WINDOW
9π
enter −
for Xmin
4
9π
enter
for Xmax
4
π
enter
for Xscl
4
enter -3 for Ymin
enter 3 for Ymax
enter 1 for Yscl
Rodgers, K.
62
Chapter 4
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press GRAPH
π

The x-values where sin x +  = 0 will be the x-values of the vertical asymptotes.
4
1
in Y2 . Press GRAPH.
Now enter
π

sin x + 

4
π
1

. Turn off the
The graph of y = csc  x +  is the same as the graph of y =
π

4
sin x +

4
π

graph of y = sin x +  . Press GRAPH.
4
Interpret the graph. The straight lines are not part of the graph and if you put your
calculator in Dot MODE, you will see the lines disappear. The lines appear to be
vertical asymptotes; they are not, but they are very close to vertical lines.
63
Chapter 4
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Section 4.4
The directions for question 7 state that one complete cycle of the graph of an
equation containing a trigonometric function is given and asks you to find an equation
to match the graph. The shape of the curve in question 7 suggests you use the
general cosine equation y = k + Acos(Bx + C) . By inspection, the curve has amplitude
of 3; this tells you that A equals 3. The period is 2π; this tells you that the value for B
is one. There is no phase shift and not vertical translation; hence both C and k are
zero. Replacing the letters with the correct values gives you the equation for the
function as y = 3(cosx ) . Now use your calculator to check your work.
press
enter
press
enter
enter
enter
enter
enter
enter
press
y=
3cos(x ) in Y1
WINDOW
0 for Xmin
2 π for Xmax
π
for Xscl
2
-3 for Ymin
3 for Ymax
1 for Yscl
GRAPH
Set the WINDOW to match the graph in the text.
Compare your calculator screen with the graph in your text. If your equation is
correct, your graph should match the graph in your text. Press TRACE.
By using the TRACE feature, you can check major points of the graph to see if they
are correct. For example, the preceding calculator screen showed the coordinates of
π
the point where the x-value is
(1.5707963). The calculator returned a y-value of
2
π
zero which matches with the y-value of
in the text. Check several key points
2
Rodgers, K.
64
Chapter 4
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before deciding that your equation is correct. Remember that once you have pressed
TRACE, you may enter the x-value you wish to check. You do not have to use the
CALC feature even though that is an acceptable procedure for finding the y-value
when a specific x-value is given.
Try question 19. The curve appears to be the sine curve turned upside down.
Mathematically speaking the sine curve has been reflected about the x-axis and the
A-value will be negative. From inspection you see that amplitude is 3; the period is 2;
and there is no phase shift or vertical translation. To find the value for B recall that
2π
the period equals
. Your paper-pencil work should resemble the following.
B
2=
2π
B
2B = 2π
B= π
The general equation for the sine function is y = k + Asin(Bx + C) . Inserting numerical
values for the letters gives the equation y = −3sin ( πx + 0 ) or y = −3sin(πx) . Check
your work by entering this equation in your calculator. Set the calculator window to
match the settings used in the text. Your y = screen; WINDOW settings; and graph
should resemble the following.
Now use the TRACE feature to verify key points of the graph. For example find the yvalue when x is 1. You know from looking at the graph in the text, that the answer is
zero. Now check your graph.
Continue checking key points until you are sure you have the correct equation.
65
Chapter 4
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Problem Set 4.5
Before using your calculator for question 3, analyze the function analytically. Given
y = 2 − cos(x ) , you note that the A-value is -1; the B-value is 1; the C-value is 0; and
the k-value is 2. Because A is negative, the graph is reflected about the x-axis; since
B is one, the period is 2π; because C is zero there is no phase shift; and since k is 2,
each y-value is increased by 2 (a vertical shift up 2 units). Compare your graph with
the following calculator screens. The x-minimum and maximum values for the
WINDOW setting are given in the text; the y-minimum and maximum values are
determined by the amplitude and vertical shift. (You could use 1 and 3; however it is
helpful to have space above and below the curve.) Negative one and four are suitable
values for the minimum and maximum y-values, but certainly not the only acceptable
values.
Question 25 asks you to generate a table of values for
π
from 0 to 4π . You should first generate this table by
y = x sin(x ) using multiples of
2
hand and then use the following keystrokes to verify your table. (Your calculator
should be in radian mode.)
Y=
x sin(x ) in Y1
TBLSET
0 in TblStart
π
enter
in ∆Tbl
2
press TABLE
press
enter
press
enter
From the table, you know the coordinates of some of the points on the graph of the
function. For example, (0,0), (1.5708,1.5708), (3.1416,0), etc. are coordinates of
points on the graph of the function. Now graph the function and verify your findings.
Rodgers, K.
66
Chapter 4
TI-83
Section 4.6
 3
Question 5 asks you to find sin −1   and to write the answer in radians.
 2 
press MODE
select Radians
press ENTER
press SIN −1
3
enter
2
press ENTER
Interpret your answer of 1.047197551. Your calculator is telling you if the sine of
3
, the measure of the angle is 1.047197551 radians. Check your
some angle is
2
answer.
press SIN
press ANS
press ENTER
3
to a decimal
2
so you can compare your answers. From the preceding screen, you see that your
answer is correct.
The calculator gave the answer as a decimal so you need to convert
67
Chapter 5
Identities and Formulas
Problem Set 5.1
The directions for this problem set ask you to prove that the identities are true.
Basically this is a paper-pencil exercise; however, there are times the calculator can
let you know if you are correct. For example, look at the identity given in question
17.
cos 4 t − sin4 t
= cot2 − 1
sin2 t
Your text suggests that you start with what appears to be the more complicated side
and through a series of substitutions and simplifications make it identical to the other
side. The following is one way to prove this identity. The calculator is going to be
used after each step to support the paper-pencil work.
press Y =
enter cot 2 t − 1 in Y1
enter
cos 4 t − sin4 t
in Y2
sin2 t
press ZOOM
select ZTrig
Use x instead of t, when entering this in
your calculator.
This will give you a general trigonometric
window which is sufficient for checking this
identity. (Either press # 7 or ENTER after
you have moved the cursor to ZTrig.)
Note. You noticed that the calculator continued to graph even though you could not
see a new graph appearing. Actually the calculator graphed what was in Y1
which you could see. Then the calculator graphed what was in Y2 , but you
could not see this because the graph was on top of the first graph. You knew
the calculator was still working because there was a short line moving up and
down in the upper right corner. This is not a proof that the two expressions are
68
Chapter 5
TI-83
identities; however, it is a strong indication. Use the up and down arrows to
see if the y-values change. Notice that the y-values do not change.
Now work with simplifying the left side of the given identity. Remember that your goal
is to simplify this to match the right side of the identity.
cos4 t − sin4 t
=
sin 2 t
(cos
2
)(
t − sin 2 t cos 2 t + sin 2 t
)
2
sin t
Since cos 2 t + sin2 t = 1, make this substitution.
(cos
2
)
t − sin 2 t 1
2
sin t
Now enter this in expression in Y2 . You are comparing the graph of
(cos
2
)
t − sin 2 t 1
sin2 t
cos4 t − sin4 t
to the graph of the orginal expression,
.
sin2 t
If the graphs are identical, you have the reassurance that your paper-pencil work is
correct.
It appears you still have not made a mistake. Continue with your paper-pencil work.
(cos
2
)
t − sin 2 t 1
2
sin t
(cost − sin t)(cost + sin t)
sin 2 t
(cos
2
)
t − sin 2 t
2
sin t
You might want to factor the numerator again.
You are not wrong; however it does not help you.
Try writing as the difference of two fractions.
(cos t )− (sin t)
2
sin 2 t
2
sin 2 t
Now enter this in expression in Y2 and compare the two graphs.
Rodgers, K.
69
Chapter 5
TI-83
You work appears to still be correct. Continue!
(cos t )− (sin t )
2
2
2
2
Substute
2
sin t
(cos t ) and 1 for (sin t ).
cot (t ) for
sin t
2
2
2
sin t
2
sin t
cot 2 (t ) − 1
You are finished. Through a series of substitutions you have converted the left side to
the same form as the right side. The benefit of the graphing calculator was to support
your work and to let you know if you had made a mistake along the way.
Question 75 asks you to find a value of θ that makes the following statement false.
sinθ =
(1 − cos θ)
2
press Y =
enter sinθ in Y1
enter
(1 − cos θ) in Y
2
2
press GRAPH
Interpret your graph. Any x-value where the two graphs are not identical is an x-value
(
)
that would make sinθ = 1 − cos2 θ false. For example, when
π
2
x = − , the sin(x) is -1 and 1-cos x is +1.
2
Use the TRACE and CALC features of the calculator to find these values.
Remember that it only takes one counterexample to prove that these two expressions
are not identities.
(
Rodgers, K.
)
70
Chapter 5
TI-83
Problem Set 5.2
Question 1 asks you to find an exact value for sin15 . Your calculator will only give
you a decimal approximation; however, you can use it to check your answer. After
you have completed your paper pencil work, convert your answer to a decimal and
compare it with the decimal approximation from your calculator.
press
select
press
press
press
enter
press
MODE
Degree
ENTER
CLEAR
SIN
15
ENTER
Problem Set 5.3
Question 17 asks you to graph y = 4 − 8sin2 x from x = 0 to x = 2π.
press MODE
select radian
press ENTER
press Y =
2
enter 4 − 8(sin(x )) in Y1 Note the use of parenthesis.
press WINDOW
enter 0 for Xmin
This value was given to you in the directions.
This value was given to you in the directions.
enter 2π Xmax
π
enter
for Xscl
2
enter -8 for Ymin
enter 8 for Ymax
enter 1 for Yscl
press GRAPH
Rodgers, K.
71
Chapter 5
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Note. You can easily translate your calculator graph to a paper-pencil graph if you
know the window settings. For example, in the above graph since you know
π
the x-scale is , you can identify the x-intercepts very quickly and translate
2
these to your paper. You also know the y-scale is one so you can very quickly
identify the y-intercept and the amplitude.
Problem Set 5.4
Question 27 asks you to graph y = 4sin
2x
from x = 0 to x = 4π.
2
Note. The important thing for you to remember when entering this problem in the
calculator is the correct use of parentheses. You are given the minimum and
maximum x-values. You should probably start with a minimum y-value of -4
and a maximum y-value of 4 since the amplitude is 4. Recognize you are
squaring the sine values which will yield only positive results.
Your calculator screens should resemble the following.
Does your calculator screen appear to be blank when you pressed GRAPH? Are you
in degree mode? If so change to radian mode to get the following screen.
The graph supports your analytical work that the graph of this function is never
negative.
Rodgers, K.
72
Chapter 5
TI-83
Question 37 asks you to prove an identity. Remember the calculator will not prove
the identity for you, but the graphing capabilities will help you determine if you have
an identity. Refer back to the beginning of Chapter 5 for an example of using the
graphing calculator to assist you in proving identities.
Rodgers, K.
73
Chapter 6
Equations
Problem Set 6.1
Question 13 asks you to solve 4 sinθ − 3 = 0 in the interval 0° ≤ θ < 360° to the
nearest tenth of a degree.
You should first do the paper-pencil work to isolate θ . Your work should resemble
the following.
4 sinθ − 3 = 0
4 sinθ = 3
sinθ =
sin −1
3
4
 3
=θ
 4
After you have done the preceding work, use the following keystrokes to complete the
task of finding the correct value for θ .
press
select
press
press
press
MODE
Degree
ENTER
CLEAR
SIN −1
3
enter
4
press ENTER
The directions asked you to round your answer to the nearest tenth of a degree.
Certainly you can do that; however, if you wish the calculator to give the answer to
you to the nearest tenth of a degree use the following keystrokes.
74
Chapter 6
TI-83
press MODE
select 1 decimal place
press ENTER
press CLEAR
press 2nd ENTER
This will recall your preceding work so you will not
have to reenter the expression.
press ENTER
Interpret your answer. You have found a value for θ such 4sin ( 48.6 ) − 3 ≈ 0 . (The
approximately equal symbol was used instead of the equal sign since the value for θ
was rounded to tenths.) Is this the only value for θ in the interval 0° ≤ θ < 360° that
will make 4 sin θ − 3 = 0 . One way to answer this question is to look at the graph.
press Y =
enter 4 sinx − 3 in Y1
press WINDOW
enter 0 for Xmin
enter 360 for Xmax
enter 10 for Xscl
enter -8 for Ymin
When you enter the expression in the calculator,
use the variable x instead of θ to represent the
angle.
Remember you are in degrees and the interval for
the solution is 0° ≤ θ < 360°.
An estimate for the minimum y-value is amplitude
plus the vertical shift. For this problem
that would be -7; however, it is usually wise to
make the window just a little larger.
enter 4 for Ymax
press ENTER
The graph clearly is equal to zero in two places. Earlier you had only found
one value. There are two answers to the equation because the sine function is
positive in both the first and second quadrants. You found the reference angle to be
Rodgers,K.
75
Chapter 6
TI-83
48.6°, which is in the first quadrant. The angle in the second quadrant would be 180° 48.6° or 131.4°.
You could have found this value from the graph by using the following keystrokes.
press GRAPH
press CALC
select zero
.
Your screen should resemble the one above. If not use the arrows until the
cursor is to the left of the x intercept.
press ENTER
Use the right blue arrow until the cursor is to the right of the x-intercept. You
do not have to have the exact x-value for the right bound that is shown on the
preceding screen.
press ENTER
The calculator is asking you to guess. What the calculator needs is for you to
trace as close to the x-intercept as possible and then press ENTER.
76 Rodgers,K.
Chapter 6
TI-83
Interpret the screen. You have found a second value in this interval for θ that makes
4 sin θ - 3 = 0 a true statement.
You are almost finished; however, whenever time permits check your answers.
Return to the Home Screen and use the following keystrokes.
enter 4 sin(48.6) -3
press ENTER
Interpret the 4.4 E-4. It means -0.0004. You wanted the answer to be zero. Even
though this is a very small number it is not zero. Recall you rounded θ to the nearest
tenth of a degree. That is why your answer is not exactly equal to zero.
Now check the second value of θ .
You got the same answer. Again, if you had not rounded θ , you would have
gotten a zero for the answer. Look at the following screen. The angle θ was not
rounded. This θ -value gives the exact value of zero when checking.
Note. There are many key concepts illustrated in this problem. You should
understand how to find all of the angle values both analytically and graphically
within a given interval.
Question 23 asks you to give exact values. As you know, the calculator cannot
always give you exact answers; however, the calculator can tell you how many xvalues will make the equation a true statement in the given interval.
Rodgers,K.
77
Chapter 6
TI-83
press MODE
select Radian
press ENTER
press CLEAR
press Y =
enter sin(x ) + 2 sin(x ) cos(x ) in Y1
press WINDOW
enter 0 for Xmin
Remember you are in radians and the
interval for the solution is 0 ≤ x < 2π.
enter 2π for Xmax
π
for Xscl
enter
6
enter -4 for Ymin
enter 4 for Ymax
press GRAPH
In the interval from 0 to 2π, the graph crosses the x-axis five times. That tells
you that there are five x-values that will satisfy the equation,
sin(x ) + 2 sin(x )cos(x ) = 0 . You should find those x-values analytically and
then use your graph to support your answers or to check your answers on the
Home Screen.
Question 33 asks you to use the quadratic formula to find all solutions in the interval
0° ≤ θ < 360°. If you have the quadratic program in your calculator, use the following
sequence of strokes to solve this problem. If you do not have the quadratic program
in your calculator, go to Appendix A for a copy of the program.
press PRGM
PRGM is for program
select QUAD
Select the quadratic program. You may have used
a different name for the program.
press ENTER
78 Rodgers,K.
Chapter 6
TI-83
press ENTER
Yes, press ENTER a second time.
The program is asking you for the A-value. Question 33 is 2 sin2 θ − 2 sinθ − 1 = 0 .
Hence the A-value is 2, the B-value is -2, and the C-value is -1.
enter
press
enter
press
enter
press
2
ENTER
-2
ENTER
-1
ENTER
You are not finished! The two x-values given are values for the sin θ , not just θ . Is it
possible to find SIN − 1 (1.366025404)? Recall the range for the SIN − 1 function is
-1 ≤ x ≤ 1. Hence you disregard any values greater than 1. Now go to the second
value for x.
SIN − 1 (-0.3660254038)
Use your calculator to find the answer to this expression.
Remember you are looking for the answer in degrees. Check your MODE.
You have found the reference angle. You also know the sine function is
negative in the third quadrant and the fourth quadrant. To get the answer in the third
quadrant, add 180° to the absolute value of the reference angle, and to get the
answer in the fourth quadrant add 360° to the reference angle.
Rodgers,K.
79
Chapter 6
TI-83
Your two answers are 201.5° and 338.5°.
Support your answer graphically.
The graph shows two answers. Use the CALC feature to see if your answers match
the x-intercepts on the graph.
press CALC
select zero
Use the left blue arrow and make sure the cursor is on the left side of the x-intercept.
press ENTER
Use the right blue arrow and move the cursor to the right of the x-intercept.
press ENTER
80 Rodgers,K.
Chapter 6
TI-83
Use the arrows and move the cursor close to the x-intercept and press ENTER.
This supports your first answer. Repeat the process and check your second answer.
Question 47 asks you to find all degree solution(s) for the equation
3
.
Your preliminary paper-pencil work should resemble the
cos 2A − 50 =
2
following.
 3
 = 2A − 50
COS− 1
 2 
 3
 . Check the MODE to make sure
Use your calculator to find a value for COS− 1
 2 
your calculator is in degree mode.
(
)
press COS− 1
 3
enter  
 2 
press ENTER
The angle measuring 30° is in the first quadrant. The cosine function is also positive
in the fourth quadrant; the angle measure would be 330°. Now use these two values
to complete your paper-pencil calculations.
Rodgers,K.
81
Chapter 6
TI-83
 3
 = 2A − 50
COS−1
 2 
 3
 = 30°
Using COS −1
 2 
30 + 360°k = 2A − 50°
(k is an integer)
80° + 360 k = 2A
80° 360 k
+
=A
2
2
40 + 180°k = A
 3
 = 330°
Using COS −1
 2 
330° + 360°k = 2A − 50°
380° + 360°k = 2A
380° 360°k
+
=A
2
2
190° + 180°k = A
Simplified
10° +180°k = A
Now use your calculator to support your answer.
press Y =
enter cos(2X − 50) in Y1
enter
press
enter
enter
enter
enter
enter
enter
press
3
in Y2
2
WINDOW
0 for Xmin
360 for Xmax
10 for Xscl
-2 for Ymin
2 for Ymax
1 for Yscl
GRAPH
82 Rodgers,K.
You will have to use the letter X instead of A. There
is no need to use the degree symbol; however,
make sure your calculator is in degree mode.
Chapter 6
TI-83
Interpret the graph. You can do this by viewing the TABLE.
press TBLSET
enter 0 for TblStart
enter 10 for ∆ Tbl
press TABLE
From the TABLE you can see when x = 10° and x = 40° the answer is .86603, the
3
. Your graph and TABLE-values support your analytical
decimal representation for
2
work. There were four points of intersection on the graph. How do you explain the
other two points? You found one solution to be 10°, the next solution is 10° + 180°k
where k is an integer. Let k = 1. The next x-value should be 190° . Check your
graph.
press GRAPH
press TRACE
enter 190
press ENTER
190° does check. The other point of intersection should occur at 40° + 180° k ;
let k = 1. The next value would be 40° + 180° or 220°.
press GRAPH
press TRACE
enter 220
press ENTER
Rodgers,K.
83
Chapter 6
TI-83
This answer also checks.
Problem Set 6.2
Question 13 asks you to solve cos(2x ) − 3sin(x ) − 2 = 0 for 0 ≤ x < 2π giving only exact
values for x. Your preliminary paper-pencil work should resemble the following.
cos(2x ) − 3sin(x ) − 2 = 0
cos(2x ) = 1− 2sin (x )
2
Recall the double angle identities.
1 − 2sin (x ) − 3sin(x ) − 2 = 0
2
−2sin 2 (x ) − 3sin(x ) − 1 = 0
2 sin2 (x ) + 3sin(x ) + 1 = 0
(2 sin(x ) + 1)(sin(x ) + 1) = 0
Set each factor equal to zero.
(2 sin(x ) + 1) = 0
sin(x ) = −
1
2
 1
SIN−1 −  = x
 2
x=
11π
7π
or
6
6
press
select
press
press
press
enter
press
enter
enter
or
(sin(x ) + 1) = 0
or
sin(x) = −1
or
SIN (−1) = x
or
-1
x =
3π
2
MODE
Radian
ENTER
CLEAR
Y=
cos(2x ) -3sin(x) - 2 in Y1
WINDOW
0 for Xmin
2π for Xmax
π
enter
for Xscl
6
84 Rodgers,K.
Chapter 6
enter
enter
enter
press
TI-83
-8 for Ymin
2 for Ymax
1 for Yscl
GRAPH
You are looking for the x-values that make the equation equal zero. It is difficult to
see that from this graph. For this problem it is not necessary to see a complete
graph; hence change the minimum and maximum y-values in the WINDOW.
enter
enter
enter
press
-1 for Ymin
1 for Ymax
1 for Yscl
GRAPH
Again, you do not see a complete graph; however, you only need to see the interval
where the graph is crossing the x-axis.
press TRACE
7π
enter
6
press ENTER
7π
, one of the x-values you found analytically, to a decimal and
6
compare this answer with the zero you found graphically. You see that both answers
are the same. Use the same sequence of keystrokes and check the other two xvalues that you found analytically.
Convert
Question 33 asks you to solve 6cos(θ ) + 7 tan(θ) = sec(θ ) in the interval 0° ≤ θ < 360°.
To find the answer analytically, use trig identities to convert the tangent and secant
functions to sine and cosine functions. . To solve this equation graphically, enter the
left side of the equation in Y1 and the right side of the equation in Y2 . (Use the original
Rodgers,K.
85
Chapter 6
TI-83
equation. If you have made an error in the conversion to sines and cosines, you want
to find it.) Make sure your calculator is in degree mode. Compare your calculator
screens with the following screens.
It is difficult to interpret the graph. Try cleaning up the graph by going to Dot MODE.
There appears to be two solutions for x in this interval. Remember you are trying to
find x-values where 6 cos ( x ) + 7 tan ( x ) = sec ( x ) ; that is you are trying to find x-values
where the two curves intersect. Find the points of intersection using the CALC feature
of your calculator and then compare this with your analytical work.
Continue to use your calculator to support your analytical work.
Problem Set 6.3
Question 7 asks you to find all exact numerical solutions for
1
sin(2x ) =
if 0 ≤ x < 2π. After you have solved this problem analytically, use your
2
calculator to support your work.
press
select
press
select
press
MODE
Radian
ENTER
Connected
ENTER
86 Rodgers,K.
Chapter 6
TI-83
press Y =
enter sin(2x ) in Y1
1
in Y2
enter
2
Set your window and then graph.
From the graph, you see four points of intersection. This tells you that there are four
1
a true statement in the interval 0 ≤ x < 2π .
x-values that will make sin(2x ) =
2
ALERT. This problem set is asking for some answers in degrees and others in
radians. Continually check to make sure your calculator is in the correct MODE.
Problem Set 6.4
Question 1 asks you to eliminate the parameter and to sketch the graph, given
x = sin(t )
y = cos(t )
Recall sin 2 (t ) + cos 2 (t ) = 1 . Now use substitution.
x2 + y 2 = 1
Support your answer graphically. First enter the parametric equations.
press MODE
select Radian
press ENTER
select Par
press ENTER
press Y =
enter sin(t ) in X1T
enter cos(t ) in Y1T
press WINDOW
enter 0 in Tmin
enter 2π in Tmax
Rodgers,K.
87
Chapter 6
enter
enter
enter
enter
enter
enter
enter
press
TI-83
π
in Tstep
12
-3 in Xmin
3 in Xmax
1 in Xscl
-2 in Ymin
2 in Ymax
1 in Yscl
GRAPH
Is this graph identical to the graph of x 2 + y 2 = 1 ?
Use the following keystrokes. Recall from your algebra studies that x 2 + y 2 = 1 is a
circle with the center at (0,0) and has a radius of 1.
press Y =
turn off the graphs
press
press
select
press
enter
QUIT
DRAW
circle
ENTER
(0,0,1)
press ENTER
press Y =
88 Rodgers,K.
(Use the blue arrows until the cursor is flashing on
the equal marks and press ENTER. The equal
marks should change color. Use the same
keystrokes later to turn the graph on again.)
2nd and PRGM
The information is entered as the x-coordinate of
the center, the y-coordinate of the center, and the
radius.
Press ENTER and not GRAPH, since you are
using the DRAW feature of the calculator.
Chapter 6
TI-83
turn the graphs on again
press GRAPH
Your graph supports your analytical work.
Rodgers,K.
89
Chapter 7
Triangles
You will use your calculator often to complete the exercises in Chapter 7;
however, very few new keystrokes will be needed. It is important that you learn to use
parentheses so you can enter the entire expression at one time. This practice will
minimize rounding errors.
Problem Set 7.1
Question 1 asks you to find side b, given A = 40°, B = 60°, and a = 12cm.
preliminary paper-pencil work should resemble the following.
Your
Using the Law of Sines
12
b
=
sin(40) sin(60 )
 12 
 =b
sin(60 )
 sin( 40)
Your calculator screen should mirror the last line of the preceding paper-pencil
work. Check to be sure that you are in degree mode. Compare your screen to the
screen that follows.
How can you prove to yourself that the above answer is correct? Substitute
this back in the original expression.
12
16.16755626
=
sin(40)
sin(60 )
Enter this expression in your calculator. The calculator uses Boolean logic and
will return a one if this is a true statement and a zero if this statement is false.
Chapter 7
TI-83
The calculator returned a one which tells you the statement was true.
Problem Set 7.2
Question 1 asks you to solve for B, and explain why there is no solution to this
triangle.
Given A = 30 °; b = 40 ft; and a = 10 ft
Use the Law of Sines
sin(30) sin(B)
=
10
40
 sin(30)
 = sin(B)
 10 
(40 )
2 = sin(B )
The last statement is false; sin(B) cannot be greater than one. This tells you that
there is no solution; the given conditions do not form a triangle. If you entered the
expression in your calculator, your screens would resemble the following. The screen
on the left is where the expression is entered. The screen on the right is the message
the calculator returns when you press ENTER.
Note. The error message on the top of the screen says DOMAIN. The calculator is
reminding you that you have tried to perform an operation on a value that is
not in the domain.
Problem SET 7.3
Question 1 asks you to find c, given a = 120 inches, b = 66 inches, and C = 60°.
Your preliminary paper-pencil work should resemble the following.
Rodgers, K.
91
Chapter 7
TI-83
Use the Law of Cosines.
c 2 = a 2 + b 2 − 2ab cos ( C )
c 2 = 1202 + 662 − 2 (120 )( 66 ) cos ( 60 )
c=
(120
2
+ 662 − 2 (120 )( 66 ) cos ( 60 ) )
Use parentheses and enter the above expression in your calculator.
Entering the expression all at once is much better than entering the expression in
steps. You have found the length of side c, 104.096 inches.
Problem Set 7.4
You will need to use Heron’s Formula to complete question 1.
S=
(s (s − a )(s − b )(s − c ))
Heron’s Formula:
where S stands for the area of the triangle and s is half of the perimeter
of the triangle.
Given a = 50 cm, b = 70 cm, C = 60°.
You need to know the value of c .
Use the Law of Cosines.
c =
(50
2
)
+ 702 − 2(50 )(70)cos(60°)
c = 62.44997998
Rodgers, K.
92
Chapter 7
TI-83
Now use Heron's Formula.
s =
1
(a + b + c )
2
s =
1
(50 + 70 + 62.44998)
2
s = 91.22499
S=
(91.22499(91.22499 − 50)(91.22499 − 70 )(91.22499 − 62.44998 ))
Since you will need to use the value of s several times, store this value in your
calculator.
enter
press
press
press
91.22499
STO
S
ENTER
(s (s − 50 )(s − 70)(s − 62.44998))
Interpret the calculator screen. You are saying the area of ∆ABC is
1515.54457 cm 2 .
Rodgers, K.
93
Chapter 8
Complex Numbers and Polar Coordinates
Problem Set 8.1
Question 1 asks you to simplify −16 . You should definitely master the paper-pencil
skills necessary to complete this task. You can use your calculator to check your
work.
press
select
press
press
enter
press
MODE
a + bi
ENTER
CLEAR
−16
ENTER
Note. If you are not in a + bi mode the calculator returns the following screen.
Interpret this screen. The error message is telling you there is no real solution.
Question 9 asks you to simplify −4 ⋅ −9 . Again, you should master the paperpencil skills required to work this problem and only use your calculator to check your
answer.
press
select
press
press
enter
press
MODE
a + bi
ENTER
CLEAR
−4 ⋅ −9
ENTER
94
Chapter 8
TI-83
Question 23 asks you to combine ( 7 + 2i ) + ( 3 − 4i ) .
press
select
press
press
enter
MODE
a + bi
ENTER
CLEAR
(7 + 2i ) + (3 − 4i )
The i key is above the decimal point on the
bottom row of keys.
press ENTER
Section 8.2
Question 27 asks you to write 10(cos12° +i sin12°) in standard form rounding to the
nearest hundredth. Your paper-pencil work should resemble the following.
10 ( cos12° + i sin12° )
10 ( 0.978 + i 0.208 )
9.78 + 2.08i
Use the following calculator keystrokes to check your work.
press
select
press
select
press
press
enter
press
MODE
a + bi
ENTER
Degree
ENTER
CLEAR
10(cos12° +i sin12°)
ENTER
Rodgers, K.
95
Chapter 8
TI-83
Interpret the screen. The dots to the right of the answer indicate there is more. Use
the right arrow key and scroll to the right. You will see the full answer.
However, since you were asked to round to hundredths, you could simply tell your
calculator to round the answer before you start.
press
select
press
press
press
press
MODE
2 (This is the 2 to the right of Float.)
ENTER
CLEAR
2nd and ENTER
ENTER
This answer matches the answer from the paper-pencil work.
Question 47 asks you to write the complex number 3 + 4i in trigonometric form. To
complete this task, you must know the value of the modulus (r) and the argument (θ) .
After you have found these values, the trigonometric form of the complex number is
r ( cos θ + i sin θ ) .
press MODE
select Float
You will need to select Float if you still have your
calculator set to two decimal places from the
previous problem.
press ENTER
select a + bi
press ENTER
Rodgers, K.
96
Chapter 8
select
press
press
press
select
enter
press
press
select
enter
press
TI-83
Degree
ENTER
CLEAR
ANGLE
R Pr(
3,4)
ENTER
ANGLE
R Pθ (
3,4)
ENTER
Returns r, given x and y.
Returns θ , given x and y.
Now translate your screen to give the trigonometric form for the complex number
3 + 4i . The r-value is 5 and the angle measure ( θ ) is 53.13D . The trigonometric form
is 5(cos53.13° + i sin53.13°). Do you want to check your answer? Use the following
keystrokes.
press ANGLE
select P Rx(
enter 5,53.130235)
press ENTER
press ANGLE
select P Ry(
Returns x, given r and θ .
You could enter only two decimal places, but your
answer would not be as accurate.
Returns y, given r and θ .
If you do not see P Ry, use the down arrow and
scroll down.
enter 5,53.130235)
press ENTER
Your answer was correct. You got three for the x-value and four for the y-value.
Rodgers, K.
97
Chapter 8
TI-83
Section 8.3
Question 1 asks you to multiply two complex numbers in trigonometric form and to
leave the answer in trigonometric form. Your calculator will multiply the two complex
numbers; however, it will return the answer in complex standard form. If you wanted
to check an answer, you could multiply using the calculator and then convert the
answer to trigonometric form.
You have found the answer in a + bi form. Now change this back to trigonometric
form. That is write the complex number 7.713 + 9.193i in trigonometric form. To
complete this task, you must know the value of the modulus (r) and the argument (θ) .
After you have found these values, the trigonometric form of the complex number is
r ( cos θ + i sin θ ) .
Before starting make sure your calculator is in a + bi and degree form.
press
select
enter
press
press
select
enter
press
ANGLE
R Pr(
7.713, 9.193)
ENTER
ANGLE
R Pθ (
7.713, 9.193))
ENTER
Returns r, given x and y.
Returns θ , given x and y.
Note. Your answer is an approximate answer since the x and y values were rounded
to three decimal places.
Section 8.4
Question 1 asks you to find two square roots for the complex number
4(cos30° +i sin30°). Your paper-pencil work should resemble the following.
Rodgers, K.
98
Chapter 8
wk
TI-83
=
=
1 
 30 + 360 k 
 30 + 360 k  
4 2  cos 
 + i sin 

2
2





2  cos (15 + 180 k ) + i sin (15 + 180 k ) 
let k
=
0
w1
=
2  cos (15 ) + i sin (15 ) 
let k
w2
=
=
1
2 [ cos195 + i sin195]
Use your calculator to check your work. To get the concept straight, think of a simple
problem. For example, you know 9 = 3 since 32 = 9 . Use this same idea to check
one of the roots you found for the previous problem. Square the root and you should
have the original problem
press
select
press
select
press
select
press
press
enter
MODE
Degree
ENTER
Pol
ENTER
a + bi
ENTER
CLEAR
(2(cos(15) +i sin(15)))2
Alert! You must use parentheses correctly. You want the quantity to be multiplied by
two and that answer squared.
The answer the calculator gave you is in standard form and the original problem was
in trigonometric form. No problem, let the calculator convert the answer to
trigonometric form. You know from the original problem the r-value was 4 and the
angle value was 30°.
press
select
press
select
select
press
press
enter
ANGLE
R˛Pr(
MATH
CPX
real(
ENTER or #2
ANS
)
Rodgers, K.
Returns r given x and y.
Use the right arrow to scroll over to CPX.
99
Chapter 8
TI-83
enter ,
enter 2
press ENTER
The r-value returned is 4, the same as the r-value in the original problem. Now check
the angle value.
press 2nd and ENTER
Repeat theses keystrokes until your calculator recalls
(2(cos(15) +i sin(15)))2
press ENTER
Since you want to use the ANS feature of the calculator,
you must have that expression entered preceding the
time it is to be used. When you use ANS the calculator
always recall the last answer that it gave.
press ANGLE
select R˛ Pθ ( Returns θ given x and y.
press MATH
select CPX
select real(
press ANS
enter )
enter ,
enter 2
press ENTER
The angle measurement returned is 30°, the same angle-value as in the original
problem.
Note. This is just one of several ways you could use your calculator to check this
problem.
Rodgers, K.
100
TI-83
APPENDIX A
Quadratic Program
PROGRAM: QUADFORM
:Disp “QUADRATIC”
:Disp “FORMULA”
:Disp “ AX2 + BX + C = 0”
:Disp: “A”
:Input A
:Disp “B”
:Input B
:Disp “C”
:Input C
2
: B − (4AC) → D
(
)
:If D < 0
:Goto 1
(( (D))/(2A))→ P
: ((−B − (D))/(2A))→ Q
: −B +
:Disp “REAL ROOTS”
:Disp “ROOT 1”
:Disp P
:Disp “ROOT 2”
:Disp Q
:Goto 2
:Lbl 1
:Disp “COMPLEX ROOTS”
: (−B /(2A)) → W
:
( (ABS (D))/(2A))→ Z
:DISP “REAL PART”
:DISP W
:DISP “IMG PART”
:DISP Z
:GOTO 2
:LBL 2
K. Rodgers
101
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