I. Function Keys
H. Trigonometry Keys
There are three trigonometric functions and three inverse trigonometric functions that are built into the TI86. The MODE (radian/degree) will affect the output of the trigonometric functions. In radian mode, you will often use . You can access by entering .
1. (sine) (cosine) (tangent) keys are the main trigonometric keys. You can evaluate these functions for any real number for which the function is defined. The mode will determine the output, so it is important that you check the setting before evaluation of the function.
Radian Mode
Sine Cosine Tangent2. Cosecant, Secant, and Cotangent are not built in to the TI86, so you will have to use the reciprocal key or put the expression in rational form to evaluate. You have to be careful with coefficients. The coefficients should not be placed in the denominator.
Radian Mode
csc(3.1) 4sec(5.1) 2cot(1.5)
3. are the three trigonometric inverse functions that are built into the TI86. The mode (radian/degree) will determine the output.
(a) The input for must be in the interval [1,1] and the output will be in the range in radian mode and the output will be in degree mode. If you enter a number outside the range [1,1], you will get an answer in complex mode which means there is no real number answer.
Radian
Mode

Degree
Mode

Error
for wrong entry.

(b) The input for the function must be in the range [1,1]. The output in radian mode will be in the range and will be in the range in degree mode. If you enter a number outside the range [1,1], you will get an answer in complex mode, which means there is no real number answer.
Radian
Mode

Degree
Mode

Mix
functions.

(c) The input for can be any real number. The output will be in the range in radian mode and in degree mode.
Radian
Mode

Degree
Mode

Mix
functions.
