If $x + y + z = {180^o},$ then $\cos 2x + \cos 2y - \cos 2z$ is equal to
$4\sin x.\,\sin y.\,\sin z$
$1 - 4\sin x.\,\sin y.\,\cos z$
$4 sin x. sin y. sin z -1$
$\cos A.\cos B.\cos C$
Given that $\cos \left( {\frac{{\alpha - \beta }}{2}} \right) = 2\cos \left( {\frac{{\alpha + B}}{2}} \right)$, then $\tan \frac{\alpha }{2}\tan \frac{\beta }{2} $ is equal to
$96 \cos \frac{\pi}{33} \cos \frac{2 \pi}{33} \cos \frac{4 \pi}{33} \cos \frac{8 \pi}{33} \cos \frac{16 \pi}{33}$ is equal to$......$.
If $\sin A + \cos A = \sqrt 2 ,$ then ${\cos ^2}A = $
If $A$ lies in the third quadrant and $3\ tanA - 4 = 0$ , then find the value of $5\ sin\ 2A + 3\ sinA + 4\ cosA$
The value of $\cos 15^\circ - \sin 15^\circ $ is equal to