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