Question
Prove that $4\text{A}=4\sin\text{A}\cos^3\text{A}-4\cos\text{A}\sin^3\text{A}.$

Answer

$\text{L.H.S.}=\sin4\text{A}$
$=2\sin2\text{A}-\cos2\text{A}=2(2\sin\text{A}\cos\text{A})(\cos^2\text{A}-\sin^2\text{A})$
$=4\sin\text{A}.\cos^3\text{A}-4\cos\text{A}\sin^3\text{A}=\text{R.H.S.}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free