If $\left|\begin{array}{ccc}\operatorname{cosec} \alpha & 1 & 0 \\ 1 & 2 \operatorname{cosec} \alpha & 1 \\ 0 & 1 & 2 \operatorname{cosec} \alpha\end{array}\right|=\frac{1}{2}\left(z^{3}+\frac{1}{z^{3}}\right)$,
then $z$ is equal to
(A) $\sin \alpha / 2$
(B) $\cos \alpha / 2$
(C) $\tan \alpha / 2$
(D) None of these