$sin^{2n}x + cos^{2n}x$ lies between
$-1$ and $1$
$0$ and $1$
$1$ and $2$
None of these
If $e ^{\left(\cos ^{2} x+\cos ^{4} x+\cos ^{6} x+\ldots \ldots \infty\right) \log _{e} 2}$ satisfies the equation $t ^{2}-9 t +8=0,$ then the value of $\frac{2 \sin x}{\sin x+\sqrt{3} \cos x}\left(0 < x < \frac{\pi}{2}\right)$ is
Find the general solution of $\cos ec\, x=-2$
If $\sqrt 3 \tan 2\theta + \sqrt 3 \tan 3\theta + \tan 2\theta \tan 3\theta = 1$, then the general value of $\theta $ is
Find the principal and general solutions of the equation $\sec x=2$
If $2{\tan ^2}\theta = {\sec ^2}\theta ,$ then the general value of $\theta $ is