TI-84 Plus and TI-84 Plus Silver Edition Guidebook

Displaying a Graph

When you press s, the TI-84 Plus plots the selected parametric equations. It evaluates the X and Y components for each value of

T

(from

Tmin

to

Tmax

in intervals of

Tstep

), and then plots each point defined by X and Y. The window variables define the viewing window.

As the graph is plotted, X, Y, and T are updated.

Smart Graph applies to parametric graphs.

Window Variables and Y

.VARS Menus

You can perform these actions from the home screen or a program.

• Access functions by using the name of the X or Y component of the equation as a variable.

• Store parametric equations.

• Select or deselect parametric equations.

• Store values directly to window variables.

Exploring Parametric Graphs

Free-Moving Cursor

The free-moving cursor in parametric graphing works the same as in Func graphing.

In

RectGC

format, moving the cursor updates the values of X and Y; if

CoordOn

format is selected,

X and Y are displayed.

In

PolarGC

format, X, Y, R, and q are updated; if

CoordOn

format is selected, R and q are displayed.

Chapter 4: Parametric Graphing 94

TRACE

To activate TRACE, press r. When TRACE is active, you can move the trace cursor along the graph of the equation one

Tstep

at a time. When you begin a trace, the trace cursor is on the first selected function at

Tmin

. If

ExprOn

is selected, then the function is displayed.

In

RectGC

format, TRACE updates and displays the values of X, Y, and T if

CoordOn

format is on.

In

PolarGC

format, X, Y, R, q and T are updated; if

CoordOn

format is selected, R, q, and T are displayed. The X and Y (or R and q) values are calculated from T.

To move five plotted points at a time on a function, press y | or y ~. If you move the cursor beyond the top or bottom of the screen, the coordinate values at the bottom of the screen continue to change appropriately.

Quick Zoom is available in parametric graphing; panning is not.

Moving the Trace Cursor to Any Valid T Value

To move the trace cursor to any valid

T

value on the current function, enter the number. When you enter the first digit, a

T=

prompt and the number you entered are displayed in the bottom-left corner of the screen. You can enter an expression at the

T=

prompt. The value must be valid for the current viewing window. When you have completed the entry, press

Í to move the cursor.

ZOOM

ZOOM

operations in parametric graphing work the same as in Func graphing. Only the

X

(

Xmin

,

Xmax

, and

Xscl

) and

Y

(

Ymin

,

Ymax

, and

Yscl

) window variables are affected.

The

T

window variables (

Tmin

,

Tmax

, and

Tstep

) are only affected when you select

ZStandard

. The

VARS ZOOM

secondary menu ZT/Z q items

1:ZTmin

,

2:ZTmax

, and

3:ZTstep

are the zoom memory variables for parametric graphing.

CALC

CALC

operations in parametric graphing work the same as in Func graphing. The

CALCULATE

menu items available in parametric graphing are

1:value

,

2:dy/dx

,

3:dy/dt

, and

4:dx/dt

.

Chapter 4: Parametric Graphing 95