If $\tan \theta + \sec \theta = {e^x},$ then $\cos \theta $ equals
$\frac{{({e^x} + {e^{ - x}})}}{2}$
$\frac{2}{{({e^x} + {e^{ - x}})}}$
$\frac{{({e^x} - {e^{ - x}})}}{2}$
$\frac{{({e^x} - {e^{ - x}})}}{{({e^x} + {e^{ - x}})}}$
Find the value of:
$\sin 75^{\circ}$
If $\sin A,\cos A$ and $\tan A$ are in $G.P.$, then ${\cos ^3}A + {\cos ^2}A$ is equal to
If $\cos A = \frac{{\sqrt 3 }}{2},$ then $\tan 3A = $
If $\tan A + \cot A = 4,$ then ${\tan ^4}A + {\cot ^4}A$ is equal to
$\cos 1^\circ + \cos 2^\circ + \cos 3^\circ + ..... + \cos 180^\circ = $