# How do you evaluate cos^-1(cos(-(pi)/10))?

$- \frac{\pi}{10}$
${\cos}^{- 1} \cos \left(- \frac{\pi}{10}\right)$ is the mathematical form for the expression
"the angle for which the cosine is cosine of $\left(- \frac{\pi}{10}\right)$"
So, its value is $- \frac{\pi}{10}$.