If $D_1 = \begin{vmatrix}\frac{1}{2} & \frac{1}{\sqrt{2}} & 0\\-\frac{1}{\sqrt{2}} & \frac{1}{2} & 0 \\ 0 & 0 & 1\end{vmatrix} $ and $D_2=\begin{vmatrix}\frac{1}{\sqrt{2}}& \frac{1}{2} & 0\\ -\frac{1}{2} & \frac{1}{\sqrt{2}}  & 0 \\ 0 & 0 & 1 \end{vmatrix}$, then $D_1D_2$ is equal to :

$\frac{9}{16}$