[tex]sec(x)=-\sqrt{2}\qquad
\begin{cases}
sec(\theta)=\cfrac{1}{cos(\theta)}
\end{cases}
\\ \quad \\
\cfrac{1}{cos(x)}=-\sqrt{2}\implies \cfrac{1}{-\sqrt{2}}=cos(x)
\\ \quad \\
cos^{-1}\left( \cfrac{1}{-\sqrt{2}} \right)=cos^{-1}[cos(x)]
\\ \quad \\
cos^{-1}\left(- \cfrac{1}{\sqrt{2}} \right)=x
\\ \quad \\
\textit{now, check your Unit Circle for those }\measuredangle x[/tex]
