- #1

- 32

- 0

**[SOLVED] Derivatives of Trigonometric Functions**

I need to find the critical numbers of this function:

y = cos x - sin x where -pi <= x <= pi

I found the derivative as:

dy/dx = -(sin x + cos x)

But when I equate dy/dx to zero, I get:

sin x + cos x = 0....where do I go from here?