求证sin^4x+cos^4x=1-2sin^2xcos^2x

分类: 作业答案 • 2021-12-28 14:35:16

问题描述：

答

求证sin^4x+cos^4x=1-2sin^2xcos^2x
证:sin^4x+cos^4x=(sin^2x+cos^2x)^2-2sin^2xcos^2x
=1-2sin^2xcos^2x