# What are the values and types of the critical points, if any, of #f(x)=cos^2 x - sin^2 x #?

##### 1 Answer

Apr 11, 2018

We can rewrite as

#f(x) = cos(2x)#

Which has first derivative

#f'(x) = -2sin(2x)#

This has critical points at

The graph demonstrates:

graph{(cosx + sinx)(cosx - sinx) [-16.02, 16.02, -8.01, 8.01]}

Hopefully this helps!