证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A)(1 cos(6A))应该是sin4Asin2A(1-cos2A) + cos4Acos2A(1+cos2A)=cos2A(1+cos6A)

分类: 作业答案 • 2021-12-19 11:33:34

问题描述：

证明sin(4A)sin(2A)(1-cos(2A)) cos(4A)cos(2A)(1 cos(2A))=cos(2A)(1 cos(6A))
应该是sin4Asin2A(1-cos2A) + cos4Acos2A(1+cos2A)=cos2A(1+cos6A)

答

=sin4Asin2A+cos4Acos2A-cos2A(cos4Acos2A-sin4Asin2A)
=cos2A+cos2Acos6A
=cos2A(1+cos6A)