sin6°+cos15°sin9°/cos6°-sin15°sin9°
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/16 23:11:42
sin6°+cos15°sin9°/cos6°-sin15°sin9°
sin6°+cos15°sin9°
=sin(15-9)+cos15sin9
=sin15cos9-sin9cos15+cos15sin9
=sin15cos9
cos6°-sin15°sin9
=cos(15-9)-sin15sin9
=sin15sin9-cos15cos9-sin15sin9
=-cos15cos9
所以原式
=sin15/(-cos15)
=-tan15
=√3-2
再问: cos(15-9)不是等于cos15cos9+sin15sin9吗?
再答: O,对 cos6°-sin15°sin9 =cos(15-9)-sin15sin9 =sin15sin9+cos15cos9-sin15sin9 =cos15cos9 所以原式 =sin15/cos15 =tan15 =2-√3
=sin(15-9)+cos15sin9
=sin15cos9-sin9cos15+cos15sin9
=sin15cos9
cos6°-sin15°sin9
=cos(15-9)-sin15sin9
=sin15sin9-cos15cos9-sin15sin9
=-cos15cos9
所以原式
=sin15/(-cos15)
=-tan15
=√3-2
再问: cos(15-9)不是等于cos15cos9+sin15sin9吗?
再答: O,对 cos6°-sin15°sin9 =cos(15-9)-sin15sin9 =sin15sin9+cos15cos9-sin15sin9 =cos15cos9 所以原式 =sin15/cos15 =tan15 =2-√3
cos15°sin9°+sin6°/sin15°sin9°—cos6°=
sin6+cos15*sin9/cos6-sin15*sin9
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