If $3\cos \theta  + 4\sin \theta  = 5$ then $3\sin \theta  - 4\cos \theta $ is

$\cos \frac{\pi }{5}\cos \frac{{2\pi }}{5}\cos \frac{{4\pi }}{5}\cos \frac{{8\pi }}{5} = $

If $\tan A = \frac{1}{2},$ then $\tan 3A = $

If $A$ and $B$ are complimentary angles, then :

If $\cos \theta = \frac{1}{2}\left( {a + \frac{1}{a}} \right),$then the value of $\cos 3\theta $is

If $A, B, C$ are angles of a triangle, then $\sin 2A + \sin 2B - \sin 2C$ is equal to