# How do you evaluate cos ^ -1 (- sqrt3/2)?

$x = \frac{5 \pi}{6} , x = \frac{7 \pi}{6}$
Use the unit circle, and find where cosine is equal to $\left(- \frac{\sqrt{3}}{2}\right)$
${\cos}^{-} 1 \left(- \frac{\sqrt{3}}{2}\right) = x$
$\cos x = - \frac{\sqrt{3}}{2}$
$x = \frac{5 \pi}{6} , x = \frac{7 \pi}{6}$