If $tan\ 80^o = a$ and $tan47^o = b$, then $tan37^o$ is equal to -
$\frac{{\alpha \, - \,\beta }}{{1\, + \,\alpha \beta }}$
$\frac{{\alpha \beta \, + \,1}}{{\alpha \, - \,\beta }}$
$\frac{{\alpha \beta \, - \,1}}{{\alpha \, + \,\beta }}$
$\frac{{\alpha \, + \,\beta }}{{1\, - \,\alpha \beta }}$
$\tan 75^\circ - \cot 75^\circ = $
The value of $ \cos ^{3}\left(\frac{\pi}{8}\right) \cdot \cos \left(\frac{3 \pi}{8}\right)+\sin ^{3}\left(\frac{\pi}{8}\right) \cdot \sin \left(\frac{3 \pi}{8}\right)$ is
$\frac{{\sec 8A - 1}}{{\sec 4A - 1}} = $
The value of $\tan 81^{\circ}-\tan 63^{\circ}-\tan 27^{\circ}+\tan 9^{\circ}$ is
The expression,$\frac{{\tan \,\left( {{\textstyle{{3\,\pi } \over 2}}\,\, - \,\,\alpha } \right)\,\,\,\cos \,\left( {{\textstyle{{3\,\pi } \over 2}}\,\, - \,\,\alpha } \right)}}{{\cos \,(2\,\pi \,\, - \,\alpha )}}$ $+ cos \left( {\alpha \,\, - \,\,\frac{\pi }{2}} \right) \,sin (\pi -\alpha ) + cos (\pi +\alpha ) sin \,\left( {\alpha \,\, - \,\,\frac{\pi }{2}} \right)$ when simplified reduces to :