# What are the absolute extrema of y=cos^2 x - sin^2 x on the interval [-2,2]?

${\cos}^{2} x - {\sin}^{2} x = \cos \left(2 x\right)$ which has a maximum value of $1$ (at $x = 0$) and a minimum value of $- 1$ (at $2 x = \pi$ so $x = \frac{\pi}{2}$)