Question

cos^2a-cos^4a+sin^4a​

Answer 1

$cos^2alpha-cos^4alpha+sin^4alpha=cos^2alpha(1-cos^2alpha)+sin^4alpha=\\cos^2alpha sin^2alpha+sin^4alpha=(1-sin^2alpha) sin^2alpha+sin^4alpha=\\sin^2alpha-sin^4alpha+sin^4alpha=sin^2alpha$