यदि $A + B + C = {270^o},$ तब $\cos \,2A + \cos 2B + \cos 2C + 4\sin A\,\sin B\,\sin C = $
$0$
$1$
$2$
$3$
$\cos \frac{\pi }{7}\cos \frac{{2\pi }}{7}\cos \frac{{4\pi }}{7} = $
$2\,{\sin ^2}\beta + 4\,\,\cos \,(\alpha + \beta )\,\,\sin \,\alpha \,\sin \,\beta + \cos \,2\,(\alpha + \beta ) = $
$\tan \frac{A}{2}$ बराबर है
$\tan 75^\circ - \cot 75^\circ = $
यदि $0 < x, y < \pi$ तथा $\cos x+\cos y-\cos (x+y)=\frac{3}{2}$, है, तो $\sin x+\cos y$ बराबर है