If $4{\sin ^4}x + {\cos ^4}x = 1,$ then $x =$
$n\pi $
$n\pi \pm {\sin ^{ - 1}}\frac{2}{5}$
$n\pi + \frac{\pi }{6}$
None of these
If $\tan \theta + \tan 2\theta + \sqrt 3 \tan \theta \tan 2\theta = \sqrt 3 ,$ then
If $\tan (\pi \cos \theta ) = \cot (\pi \sin \theta )$, then $\sin \left( {\theta + \frac{\pi }{4}} \right)$ equals
If $\cos 2\theta + 3\cos \theta = 0$, then the general value of $\theta $ is
The number of integral values of $k$, for which the equation $7\cos x + 5\sin x = 2k + 1$ has a solution, is
The solution of $3\tan (A - {15^o}) = \tan (A + {15^o})$ is