Find the principal value of the following: $cos^{-1} \bigg( -\frac {1} {\sqrt 2} \bigg) $

Question

$\begin{array}{1 1} \frac{3\pi}{4} \\ -\frac{3\pi}{4} \\ \frac{\pi}{4} \\ - \frac{\pi}{4} \end{array} $