证明sin^4x-cos^4x=sin^2x-cos^2x
问题描述:
证明sin^4x-cos^4x=sin^2x-cos^2x
答
sin^4x-cos^4x=(sin^2x-cos^2x )(sin^2x+cos^2x)
=(sin^2x-cos^2x )*1=(sin^2x-cos^2x )