# Knowledge Base

## Solution 12650: Calculating Trigonometric Functions on the TI-81.

### How do I input and calculate trigonometric functions on the TI-81?

The TI-81 can display the results of these calculations in both Radian and Degree mode.

For Degrees:

1) Press the [MODE] key. Press the [down arrow] key 2 times.
2) Highlight Deg and press the [ENTER] key, this changes the mode from a default of radian to degree for the measurement of angles.
3) Press the [2nd] key and the [CLEAR] key to return to the home screen.
4) Sin of 30 degrees is equal to (.5) in degrees to enter this press the [SIN] key and then enter 30.
5) Next press the [ENTER] key.
6) Cosine of 30 degrees is equal to (.86602....) in degrees to enter this press the [COS] key and then enter 30.
7) Next press the [ENTER] key.
8) Tangent of 30 degrees is equal to (.57735.....) in degrees to enter this press the [TAN] key and then enter 30.
9) Next press the [ENTER] key.

1) Press the [MODE] key then press the [down arrow] key 2 times.
2) Highlight Rad and then press the [ENTER] key, this changes the mode from degree to radians for the measurement of angles.
3) Press the [2nd] key and the [CLEAR] key to return to the home screen.
4) Sin of p in radians is equal to (0) to enter this press the [SIN] key and [2nd] [p].
5) Next press the [ENTER] key.
6) Cosine of p in radians is equal to (-1) to enter this press the [COS] key and [2nd] [p].
7) Next press the [ENTER] key.
8) Tangent of p in radians is equal to (0) to enter this press the [TAN] key and [2nd] [p].
9) Next press the [ENTER] key.