cos^2 x - sin^2 x 是怎么化简=cos 2x

问题描述:

cos^2 x - sin^2 x 是怎么化简=cos 2x
cos^2 x - sin^2 x 是怎么化简=cos 2x的?

cos²x-sin²x
=cosxcosx-sinxsinx
=cos(x+x)
=cos2x