Question

$sin^{4}x+sin^{2}x*cos^{2}x-sin^{2}x$

Answer 1

$=sin^4x+sin^2x(cos^2x-1)=sin^4x-sin^2x(1-cos^2x)= \ \ =sin^4x-sin^2x*sin^2x=sin^4x-sin^4x=0$