化简cosα+cos(120°-α)+cos(120+α)

来源:学生作业帮助网 编辑:六六作业网 时间:2024/12/20 00:21:43
化简cosα+cos(120°-α)+cos(120+α)化简cosα+cos(120°-α)+cos(120+α)化简cosα+cos(120°-α)+cos(120+α)cosα+cos(120°

化简cosα+cos(120°-α)+cos(120+α)
化简cosα+cos(120°-α)+cos(120+α)

化简cosα+cos(120°-α)+cos(120+α)
cosα+cos(120°-α)+cos(120+α)
=cosα+(cos120cosα+sin120sinα)+(cos120cosα-sin120sinα)
=cosα+cos120cosα+sin120sinα+cos120cosα-sin120sinα
=cosα+2*cos120cosα
=cosα+2*cos(90+30)cosα
=cosα+2*(-1/2)cosα
=cosα+(-cosα)
=0

等于0