यदि $\sin \theta + \sin 2\theta + \sin 3\theta = \sin \alpha $ तथा $\cos \theta + \cos 2\theta + \cos 3\theta = \cos \alpha $, तब $\theta$ का मान होगा
$\alpha /2$
$\alpha $
$2\alpha $
$\alpha /6$
यदि $\tan A = \frac{1}{2},$ तो $\tan 3A = $
$\cos A + \cos (240^\circ + A) + \cos (240^\circ - A) = $
यदि $x\cos \theta = y\cos \,\left( {\theta + \frac{{2\pi }}{3}} \right) = z\cos \,\left( {\theta + \frac{{4\pi }}{3}} \right)$ , तब $\frac{1}{x} + \frac{1}{y} + \frac{1}{z}$ बराबर है
यदि $\cos \,(\theta - \alpha ) = a,\,\,\sin \,(\theta - \beta ) = b,\,\,$ हो, तब ${\cos ^2}(\alpha - \beta ) + 2ab\,\sin \,(\alpha - \beta )$ बराबर है
यदि $A + B + C = \pi ,$ तो ${\tan ^2}\frac{A}{2} + {\tan ^2}\frac{B}{2} + $${\tan ^2}\frac{C}{2}$ हमेशा है