作业帮cos51°cos9°-cos39°sin9°=
来源：学生作业帮助网 编辑：作业帮 时间：2024/04/29 06:35:52
cos51°cos9°-cos39°sin9°=
cos51°cos9°-cos39°sin9°=
cos51°cos9°-cos39°sin9°=
cos51°cos9°-cos39°sin9°
=cos51°cos9°-sin51°sin9°
=cos(51°+9°)
=cos60°
=1/2
明白请采纳,
有新问题请求助,
cos51°cos9°-cos39°sin9°=sin(90°-51°)cos9°-cos39°sin9°=sin31°cos9°-cos39°sin9°=sin(39°-9°)=sin30°=1/2;
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