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来源：学生作业帮助网 编辑：六六作业网 时间：2024/10/06 08:58:39
已知0已知0已知0cos(45°＋a)=sin[90°－(45°＋a)]=sin(45°－a)=1/3sin(45°-α)=1/3那么cos(45°+α)=cos[90°-(45°-α)]=sin(4
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已知0<α<45°,sin(45°-α)=1/3,则cos(45°+α)=?
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cos(45°＋a)
=sin[90°－(45°＋a)]
=sin(45°－a)
=1/3
sin(45°-α)=1/3
那么cos(45°+α)=cos[90°-(45°-α)]=sin(45°-α)=1/3
cos(45°+α)=sin（90°-（45°＋α））=sin(45°-α)=1/3