Solve this :  Please solve my queries. Do not send any links.

$\mathrm{Q}. \mathrm{Prove} \mathrm{that} {\sec }^2\mathrm{\theta } -\left[\frac{{\sin }^2 \mathrm{\theta }-2 {\sin }^4 \mathrm{\theta }}{2 {\cos }^{4 }\mathrm{\theta }-{\cos }^2 \mathrm{\theta }}\right]=1$