Question
Show thet:
$(\sin^6\text{x}+\cos^6\text{x})-3(\sin^4\text{x}+\cos^4\text{x})+1=0$

Answer

$\text{LHS}=2(\sin^6\text{x}+\cos^6\text{x})-3(\sin^4\text{x}+\cos^4\text{x})+1$
$=2\big((\sin^2)^3+(\cos^2\text{x})^3\big)-3(\sin^4\text{x}+\cos^4\text{x})+1$ $\big[\because\text{a}^3+\text{b}^3=(\text{a+b})\big(\text{a}^2\text{ab+b}^2\big)\big]$
$=2[(\sin^2\text{x}+\cos^4\text{x})(\sin^4\text{x}-\sin^2\text{x}\cos^2\text{x}+\cos^4\text{x})]-3(\sin^4\text{x}+\cos^4\text{x})+1$
$=-[\sin^4\text{x}+\cos^4\text{x}+2\sin^2\text{x}\cos^2\text{x}]+1$
$=-[\sin^2\text{x}+\cos^2\text{x}]+1$
$=-1+1$
$=0=\text{RHS}$

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