## Trigonometry (11th Edition) Clone

$s=\dfrac{\pi}{4}$
RECALL: $\frac{\pi}{4}$ is a special angle and $\cos{(\frac{\pi}{4})}=\dfrac{\sqrt2}{2}$ Thus, if $\cos{s} = \frac{\sqrt2}{2}$, then $s=\dfrac{\pi}{4}$.