Question

cos^2a-cos^4a+sin^4a​

Answer 1

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