Matrices and Determinants

If A = \left[ {\matrix{ {\cos \theta } & {i\sin \theta } \cr {i\sin \theta } & {\cos \theta } \cr } } \right], $\left( {\theta = {\pi \over {24}}} \right)$ and {A^5} = \left[ {\matrix{ a & b \cr c & d \cr } } \right], where $i = \sqrt { - 1}$ then which one of the following is not true?