# Calculator Notes for TI-82 ```CHAPTER 11 Calculator Notes for the TI-82
Note 11A • Trigonometric Functions
The trigonometric functions in this calculator will work with angles that are
measured either in degrees or in units called radians. In this course, all angles
will be measured in degrees. Press MODE and check that your calculator is set
to Degree mode.
The keys for the three trigonometric functions—sine, cosine, and tangent—are
SIN , COS , and TAN . (If you look around you might find a calculator menu with
sinh, cosh, and tanh. These are not the trigonometric functions you want to use.)
Press the key with the function you need, enter an angle measure, and press ENTER .
The output is the trigonometric ratio expressed as a decimal number.
Note 11B • Inverse Trigonometric Functions
Press
MODE
and check that your calculator is set to Degree mode.
To convert a trigonometric ratio back to an angle measure, use the inverse
function found above the same key as the function. Press 2nd , select the inverse
function, either [SIN1], [COS1], or [TAN1], enter the ratio, and press ENTER .
The output is an angle measured in degrees.
When using an inverse trigonometric function, the ratio can be entered either
as a decimal number or as a fraction. If you use a fraction, you must enclose the
ratio in parentheses to show the correct order of operations.
Often, when using an inverse trigonometric function, the degree measure of
the output angle is not a whole number.