c
$A = \left[ {\begin{array}{*{20}{c}}
{\cos \theta }&{ - \sin \theta }\\
{\sin \theta }&{\cos \theta }
\end{array}} \right]$
${A^2} = \left[ {\begin{array}{*{20}{c}}
{\cos \theta }&{ - \sin \theta }\\
{\sin \theta }&{\cos \theta }
\end{array}} \right]\left[ {\begin{array}{*{20}{c}}
{\cos \theta }&{ - \sin \theta }\\
{\sin \theta }&{\cos \theta }
\end{array}} \right]$
${A^2} = \left[ {\begin{array}{*{20}{c}}
{\cos 2\theta }&{ - \sin 2\theta }\\
{\sin 2\theta }&{\cos 2\theta }
\end{array}} \right]$
By using symmetry
${A^{ - 50}} = \left[ {\begin{array}{*{20}{c}}
{\cos \left( { - 50\theta } \right)}&{ - \sin \left( { - 50\theta } \right)}\\
{\sin \left( { - 50\theta } \right)}&{\cos \left( { - 50\theta } \right)}
\end{array}} \right]$
At $\theta = \frac{\pi }{{12}}$
${A^{ - 50}} = \left[ {\begin{array}{*{20}{c}}
{\cos \frac{{25\pi }}{6}}&{\sin \frac{{25\pi }}{6}}\\
{ - \sin \frac{{25\pi }}{6}}&{\cos \frac{{25\pi }}{6}}
\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}
{\cos \frac{\pi }{6}}&{\sin \frac{\pi }{6}}\\
{ - \sin \frac{\pi }{6}}&{\cos \frac{\pi }{6}}
\end{array}} \right]$
$ = \left[ {\begin{array}{*{20}{c}}
{\frac{{\sqrt 3 }}{2}}&{\frac{1}{2}}\\
{\frac{{ - 1}}{2}}&{\frac{{\sqrt 3 }}{2}}
\end{array}} \right]$