${\rm{cosec }}A - 2\cot 2A\cos A = $

$\tan 75^\circ - \cot 75^\circ = $

$\sin 12^\circ \sin 48^\circ \sin 54^\circ = $

$\tan 20^\circ \tan 40^\circ \tan 60^\circ \tan 80^\circ = $

$\frac{{\cos A}}{{1 - \sin A}} = $

$3\,\left[ {{{\sin }^4}\,\left( {\frac{{3\pi }}{2} - \alpha } \right) + {{\sin }^4}\,(3\pi + \alpha )} \right]$ $ - 2\,\left[ {{{\sin }^6}\,\left( {\frac{\pi }{2} + \alpha } \right) + {{\sin }^6}(5\pi - \alpha )} \right] = $