If $\tan \theta = \frac{{\sin \alpha - \cos \alpha }}{{\sin \alpha + \cos \alpha }},$ then $\sin \alpha + \cos \alpha $ and $\sin \alpha - \cos \alpha $ must be equal to
$\sqrt 2 \cos \theta ,\,\,\sqrt 2 \sin \theta $
$\sqrt 2 \sin \theta ,\,\,\sqrt 2 \cos \theta $
$\sqrt 2 \sin \theta ,\,\,\sqrt 2 \sin \theta $
$\sqrt 2 \,\cos \theta ,\,\,\sqrt 2 \,\cos \theta $
If $0 < x , y < \pi$ and $\cos x +\cos y-\cos ( x + y )=\frac{3}{2},$ then $\sin x+\cos y$ is equal to ...... .
Show that
$\tan 3 x \tan 2 x \tan x=\tan 3 x-\tan 2 x-\tan x$
$\frac{{\sqrt 2 - \sin \alpha - \cos \alpha }}{{\sin \alpha - \cos \alpha }} = $
$\frac{{\cos 12^\circ - \sin 12^\circ }}{{\cos 12^\circ + \sin 12^\circ }} + \frac{{\sin 147^\circ }}{{\cos 147^\circ }} = $
In triangle $ABC$, the value of $\sin 2A + \sin 2B + \sin 2C$ is equal to