Question

If $\sin \theta =\frac{1}{2}$, show that $(3\cos \theta -4{\cos }^3\theta )=0$

Answer 1

$\sin \theta =1/2\Rightarrow \theta =\pi /6$

$3\cos \theta -4{\cos }^3\theta =\cos 3\theta$

$=\cos 3\frac{\pi }{6}$

$=\cos \pi /2=0$