The value of $tan^{-1} (\frac{sin2 -1}{cos2})$ is equal to:-
$\frac{\pi}{2} - 1$
$2 - \frac{\pi}{2}$
$1- \frac{\pi}{4}$
$ \frac{\pi}{4}-1$
Prove that $\tan 4 x=\frac{4 \tan x\left(1-\tan ^{2} x\right)}{1-6 \tan ^{2} x+\tan ^{4} x}$
If $x + y + z = {180^o},$ then $\cos 2x + \cos 2y - \cos 2z$ is equal to
If $A + B + C = \frac{{3\pi }}{2},$ then $\cos 2A + \cos 2B + \cos 2C = $
If $A + B + C = {180^o},$ then the value of $(\cot B + \cot C)$ $(\cot C + \cot A)\,\,(\cot A + \cot B)$ will be
If $\alpha ,\,\beta ,\,\gamma \in \,\left( {0,\,\frac{\pi }{2}} \right)$, then $\frac{{\sin \,(\alpha + \beta + \gamma )}}{{\sin \alpha + \sin \beta + \sin \gamma }}$ is