If $2\sec 2\alpha = \tan \beta + \cot \beta ,$ then one of the values of $\alpha + \beta $ is
$\frac{\pi }{4}$
$\frac{\pi }{2}$
$\pi $
$2\pi $
Let $S=\left\{x \in(-\pi, \pi): x \neq 0, \pm \frac{\pi}{2}\right\}$. The sum of all distinct solutions of the equation $\sqrt{3} \sec x+\operatorname{cosec} x+2(\tan x-\cot x)=0$ in the set $S$ is equal to
$\frac{{\sin 3A - \cos \left( {\frac{\pi }{2} - A} \right)}}{{\cos A + \cos (\pi + 3A)}} = $
Prove that: $\cos 4 x=1-8 \sin ^{2} x \cos ^{2} x$
$cosec^2\theta $ = $\frac{4xy}{(x +y)^2}$ is true if and only if
$1 - 2{\sin ^2}\left( {\frac{\pi }{4} + \theta } \right) = $