Question

Помогите упростить один пример:
Sin^4a-cos^4a-sin^2a+cos^2a

Answer 1

$sin^4 alpha -cos^4alpha -sin^2alpha +cos^2alpha =\ \ =(sin^2alpha +cos^2alpha )(sin^2alpha -cos^2alpha )-sin^2alpha +cos^2alpha =\ \ =sin^2alpha -cos^2alpha -sin^2alpha +cos^2alpha =0.$