Find the principal values of the following: <br> $cos^{-1} \bigg(\large\frac { \sqrt 3} {2}\bigg)$

Question

$\begin{array}{1 1} -\frac{\pi}{6} \\ \frac{\pi}{6} \\ \frac{\pi}{\sqrt 3} \\ \frac{\pi}{2} \end{array}$