2cos(x+y)cosx-cos(2x+y)化简

来源：学生作业帮编辑：大师作文网作业帮分类：综合作业时间：2024/11/17 17:13:17

2cos(x+y)cosx-cos(2x+y)
=2cos(x+y)cosx-cos[(x+y)+x]
=2cos(x+y)cosx-cos(x+y)cosx+sin(x+y)sinx
=cos(x+y)cosx+sin(x+y)sinx
=cos[(x+y)-x]
=cosy

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