Question

Which of the following is a true statement for 0° < theta < 90°?
A. tan(theta) = -tan(theta)
B. tan(theta) = -tan(180° -theta ).
C. tan(theta)= tan(90° -theta )
D. none of the above

Answer 1

Plug numbers in for theta, the easiest way,

Answer 2

Although tan is an odd function, I'm not sure that A can be true given the domain of 0 to 90. For C, that looks suspiciously like the cofunction definition (had it been cotan(90 - theta). I would plug B into a calculator and see if it true.

Answer 3

use this identity :
tan(180° - theta ) = -tan theta

Answer 4

now both sides multiplied by -1
-1 * tan(180° - theta ) = -1 * -tan theta
- tan(180° - theta ) = tan theta

Answer 5

tan (180+theta) = tan(theta)
tan (-theta) = - tan(theta)

Answer 6

This is something you need to know. If you plug this in your options you can check wherever they true or false.