The value of $cot\, x + cot\, (60^o + x) + cot\, (120^o + x)$ is equal to :
$cot\, 3x$
$tan\, 3x$
$3\, tan \,3x$
$\frac{{3\,\, - \,\,9\,{{\tan }^2}\,x}}{{3\,\tan \,x\,\, - \,\,{{\tan }^3}\,x}}$
Prove that $\cot x \cot 2 x-\cot 2 x \cot 3 x-\cot 3 x \cot x=1$
$2\cos x - \cos 3x - \cos 5x = $
Let $\frac{\pi}{2} < x < \pi$ be such that $\cot x=\frac{-5}{\sqrt{11}}$. Then $\left(\sin \frac{11 x}{2}\right)(\sin 6 x-\cos 6 x)+\left(\cos \frac{11 x}{2}\right)(\sin 6 x+\cos 6 x)$ is equal to
If $\sin \left( {x + \frac{{4\pi }}{9}} \right) = a;\,$ $\frac{\pi }{9}\, < \,x\, < \,\frac{\pi }{3},$ then $\cos \left( {x + \frac{{7\pi }}{9}} \right)$ equals :-
$\tan 9^\circ - \tan 27^\circ - \tan 63^\circ + \tan 81^\circ = $