Answer
$\theta=0^o$
Work Step by Step
RECALL:
$y=\tan^{-1}{(x)} \longrightarrow \tan{y}=x$, $y$ is in the interval $(-90^o, 90^o)$
Thus, $\theta=\tan^{-1}{(0)}$ implies that $\tan{\theta}=0$.
Note that $\tan{(0^o)}=0$.
Therefore,
$\theta=\tan^{-1}{(0)}\longrightarrow \theta=0^o$
