# How do you find the value for cos^(-1) [(cos(135')]?

${\cos}^{- 1} \left[\cos \left(135 '\right)\right] = 135 '$
${\cos}^{- 1} \left(x\right)$ or $\arccos \left(x\right)$ is the angle, $\theta$ for which $\cos \left(\theta\right) = x$.
If $x = \cos \left(135 '\right)$ then $\theta = 135 '$
(It is unusual to have specified the angle in minutes; if it is relevant, note: $135 ' = {2}^{o} 15 '$)