The value of $4 \cos^3 20^{\circ}$ is

$\sqrt{\frac{1 - \sin A}{1 + \sin A}} = $

If $L = \sin^{2}\left(\frac{\pi}{16}\right) - \sin^{2}\left(\frac{\pi}{8}\right)$ and $M = \cos^{2}\left(\frac{\pi}{16}\right) - \sin^{2}\left(\frac{\pi}{8}\right)$,then which of the following is correct?

$\frac{1-\cos 2 \theta+\sin 2 \theta}{1+\cos 2 \theta+\sin 2 \theta}=$

$\cot x - \tan x = $

If $2 \cos \theta = x + \frac{1}{x}$,then $2 \cos 3 \theta = $