$\sqrt 2 + \sqrt 3 + \sqrt 4 + \sqrt 6 $ is equal to
$\cot 7\frac{{{1^o}}}{2}$
$\sin 7\frac{{{1^o}}}{2}$
$\sin \,{15^o}$
$\cos \,\,{15^o}$
If $\alpha + \beta - \gamma = \pi ,$ then ${\sin ^2}\alpha + {\sin ^2}\beta - {\sin ^2}\gamma = $
If $A + B + C = {180^o},$ then the value of $\cot \frac{A}{2} + \cot \frac{B}{2} + \cot \frac{C}{2}$ will be
$\frac{1}{{\tan 3A - \tan A}} - \frac{1}{{\cot 3A - \cot A}} = $
$(\sec 2A + 1){\sec ^2}A = $
$1 + \cos 2x + \cos 4x + \cos 6x = $