# How do you evaluate cos^-1(cos((5pi)/6))?

$\frac{5 \pi}{6}$
The ${\cos}^{-} 1 x$ is the inverse function of cosx
and color(red)(|bar(ul(color(white)(a/a)color(black)(cos^-1(cosx)=x)color(white)(a/a)|))
$\Rightarrow {\cos}^{-} 1 \left(\cos \left(\frac{5 \pi}{6}\right)\right) = \frac{5 \pi}{6}$