$\cos 15^\circ = $
$\sqrt {\frac{{1 + \cos 30^\circ }}{2}} $
$\sqrt {\frac{{1 - \cos 30^\circ }}{2}}$
$ \pm \sqrt {\frac{{1 + \cos 30^\circ }}{2}} $
$ \pm \sqrt {\frac{{1 - \cos 30^\circ }}{2}} $
If $\cos \theta - \sin \theta = \sqrt 2 \sin \theta ,$ then $\cos \theta + \sin \theta $ is equal to
Find the radian measures corresponding to the following degree measures:
$-47^{\circ} 30^{\prime}$
The radius of the circle whose arc of length $15\,cm$ makes an angle of $3/4$ radian at the centre is .....$cm$
Prove that :
$\cot ^{2} \frac{\pi}{6}+\cos ec \,\frac{5 \pi}{6}+3 \tan ^{2}\, \frac{\pi}{6}=6$
The product $\left(1+\tan 1^{\circ}\right)\left(1+\tan 2^{\circ}\right)\left(1+\tan 3^{\circ}\right)$ $. .\left(1+\tan 45^{\circ}\right)$ equals