1.
Let A=(cosαsinαsinαcosα)A = \begin{pmatrix} \cos\alpha & -\sin\alpha \\ \sin\alpha & \cos\alpha \end{pmatrix} (αR\alpha \in \mathbb{R}) such that A32=(0110)A^{32} = \begin{pmatrix} 0 & -1 \\ 1 & 0 \end{pmatrix}. Then a value of α\alpha is: