Answer
$\sin \theta = \sqrt{1 - x^2}$
Work Step by Step
Let $\cos ^ {–1} x = \theta$, then, $\cos \theta = x$
To evaluate, $\sin (\cos ^ {–1} x) = \sin \theta$
We know that, $\sin \theta = \sqrt{1 - \cos ^2 x}$
Using above relations we get
$\sin \theta = \sqrt{1 - x^2}$
