જો $\sin 2\theta + \sin 2\phi = 1/2$ અને $\cos 2\theta + \cos 2\phi = 3/2$, તો ${\cos ^2}(\theta - \phi  ) = $

If $k = \sin \frac{\pi }{{18}}\,.\,\sin \frac{{5\pi }}{{18}}\,.\,\sin \frac{{7\pi }}{{18}},$ then the numerical value of $k$ is

$\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } = $

સમીકરણ $\frac{{{{\tan }^2}20^\circ  - {{\sin }^2}20^\circ }}{{{{\tan }^2}20^\circ \,\cdot\,{{\sin }^2}20^\circ }}$ = 

 $tan^{-1} (\frac{sin2 -1}{cos2})$ = 

${(\cos \alpha + \cos \beta )^2} + {(\sin \alpha + \sin \beta )^2} = $