જો $\alpha $ અને $\beta $ એ સમીકરણ $sin^2\,x + a\, sin\, x + b = 0$ અને $cos^2\,x + c\, cos\, x + d = 0$ ના બીજો હોય તો $sin\,(\alpha + \beta )$ =
$\frac{{2bd}}{{{b^2} + {d^2}}}$
$\frac{{{a^2} + {c^2}}}{{2ac}}$
$\frac{{{b^2} + {d^2}}}{{2bd}}$
$\frac{{2ac}}{{{a^2} + {c^2}}}$
જો $\tan x + \tan \left( {\frac{\pi }{3} + x} \right) + \tan \left( {\frac{{2\pi }}{3} + x} \right) = 3,$ તો
$\sin {20^o}\,\sin {40^o}\,\sin {60^o}\,\sin {80^o} = $
${\sin ^2}\frac{\pi }{8} + {\sin ^2}\frac{{3\pi }}{8} + {\sin ^2}\frac{{5\pi }}{8} + {\sin ^2}\frac{{7\pi }}{8} = $
જો $A + B + C = {180^o},$ તો $\cot \frac{A}{2} + \cot \frac{B}{2} + \cot \frac{C}{2} = . . .$
જો $\frac{\sqrt{2} \sin \alpha}{\sqrt{1+\cos 2 \alpha}}=\frac{1}{7}$ અને $\sqrt{\frac{1-\cos 2 \beta}{2}}=\frac{1}{\sqrt{10}}$ $\alpha, \beta \in\left(0, \frac{\pi}{2}\right),$ તો $\tan (\alpha+2 \beta)$ મેળવો.