Prove that $\frac{\cos 4 x+\cos 3 x+\cos 2 x}{\sin 4 x+\sin 3 x+\sin 2 x}=\cot 3 x$
Prove that $\frac{\cos 4 x+\cos 3 x+\cos 2 x}{\sin 4 x+\sin 3 x+\sin 2 x}=\cot 3 x$
$L.H.S.$ $=\frac{\cos 4 x+\cos 3 x+\cos 2 x}{\sin 4 x+\sin 3 x+\sin 2 x}$
$=\frac{(\cos 4 x+\cos 2 x)+\cos 3 x}{(\sin 4 x+\sin 2 x)+\sin 3 x}$
$=\frac{2 \cos \left(\frac{4 x+2 x}{2}\right) \cos \left(\frac{4 x-2 x}{2}\right)+\cos 3 x}{2 \sin \left(\frac{4 x+2 x}{2}\right) \cos \left(\frac{4 x-2 x}{2}\right)+\sin 3 x}$
$[\because \cos A+\cos B=2 \cos \left(\frac{A+B}{2}\right) \cos \left(\frac{A-B}{2}\right),$
$\sin A+\sin B=2 \sin \left(\frac{A+B}{2}\right) \cos \left(\frac{A-B}{2}\right)]$
$=\frac{2 \cos 3 x \cos +\cos 3 x}{2 \sin 3 x \cos x+\sin 3 x}$
$=\frac{\cos 3 x(2 \cos x+1)}{\sin 3 x(2 \cos x+1)}$
$\cot 3 x=R .H .S.$
Similar Questions
$\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } = $
$\sqrt {2 + \sqrt {2 + 2\cos 4\theta } } = $
If $\tan \theta = t,$ then $\tan 2\theta + \sec 2\theta = $
If $\tan \theta = t,$ then $\tan 2\theta + \sec 2\theta = $
If $\tan \frac{\theta }{2} = t,$then $\frac{{1 - {t^2}}}{{1 + {t^2}}}$is equal to
If $\tan \frac{\theta }{2} = t,$then $\frac{{1 - {t^2}}}{{1 + {t^2}}}$is equal to
The expression $\frac{{{{\tan }^2}20^\circ - {{\sin }^2}20^\circ }}{{{{\tan }^2}20^\circ \,\cdot\,{{\sin }^2}20^\circ }}$ simplifies to
The expression $\frac{{{{\tan }^2}20^\circ - {{\sin }^2}20^\circ }}{{{{\tan }^2}20^\circ \,\cdot\,{{\sin }^2}20^\circ }}$ simplifies to
The value of $\tan 7\frac{1}{2}^\circ $ is equal to
The value of $\tan 7\frac{1}{2}^\circ $ is equal to