If $\sin\alpha=\sin\beta$ and $\cos\alpha=\cos\beta$ then

Question

$\begin{array}{1 1}(a)\;\sin\large\frac{\alpha+\beta}{2}\normalsize=0&(b)\;\cos\large\frac{\alpha+\beta}{2}\normalsize=0\\(c)\;\sin\large\frac{\alpha-\beta}{2}\normalsize=0&(d)\;\cos\large\frac{\alpha-\beta}{2}\normalsize=0\end{array}$