Answer
$\theta=\dfrac{\pi}{2}$ or $90^{\circ}$
Work Step by Step
We are given $\cos^{-1} (0)$
We know that the trigonometric function $\cos^{-1}$ has domain $[-1,1]$ and the range is: $[0, \pi]$.
So, $\theta = \cos^{-1} (0) $
This implies that: $\theta=\dfrac{\pi}{2}$ or $90^{\circ}$
