$\frac{1-\tan^2 15^{\circ}}{1+\tan^2 15^{\circ}} = ?$

If $\tan A < 0$ and $\tan 2A = -\frac{4}{3}$,then $\cos 6A =$

$\operatorname{cosec} 2 \theta - \cot 2 \theta = ?$

The value of $\cos 15^{\circ} \cos 7.5^{\circ} \sin 7.5^{\circ}$ is

$\sqrt{2} + \sqrt{3} + \sqrt{4} + \sqrt{6}$ is equal to

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?