$1 + \cos 2x + \cos 4x + \cos 6x = $
$2\cos x\cos 2x\cos 3x$
$4\sin x\,\cos 2x\cos 3x$
$4\cos x\cos 2x\cos 3x$
None of these
$\frac{{\cos 12^\circ - \sin 12^\circ }}{{\cos 12^\circ + \sin 12^\circ }} + \frac{{\sin 147^\circ }}{{\cos 147^\circ }} = $
$\frac{{\tan A + \sec A - 1}}{{\tan A - \sec A + 1}} = $
If $\cos \theta = \frac{3}{5}$ and $\cos \phi = \frac{4}{5},$ where $\theta $ and $\phi $ are positive acute angles, then $\cos \frac{{\theta - \phi }}{2} = $
The value of $\sin 600^\circ \cos 330^\circ + \cos 120^\circ \sin 150^\circ $ is
$\frac{{\sin \theta + \sin 2\theta }}{{1 + \cos \theta + \cos 2\theta }} = $