求证sin^4x-cos^4x=sin^2x-cos^2x

分类: 作业答案 • 2022-03-25 19:11:39

问题描述：

答

sin^4x-cos^4x =(sin^2x+cos^2x)(sin^2x-cos^2x)
∵sin^2x+cos^2x=1
∴sin^4x-cos^4x =(sin^2x+cos^2x)(sin^2x-cos^2x)=(sin^2x-cos^2x)