Solve the equation $\sec^22x=1-\tan 2x$
$\begin{array}{1 1}(A)\;\large\frac{n\pi}{2}- \frac{\pi}{8}&(B)\;\large\frac{n\pi}{4}- \frac{\pi}{6}\\(C)\;\large\frac{n\pi}{3}- \frac{\pi}{12}&(D)\;\large\frac{n\pi}{6}- \frac{\pi}{12}\end{array}$