sin6°+cos15°sin9°/cos6°-sin15°sin9°

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sin6°+cos15°sin9°/cos6°-sin15°sin9°sin6°+cos15°sin9°/cos6°-sin15°sin9°sin6°+cos15°sin9°/cos6°-sin15°

sin6°+cos15°sin9°/cos6°-sin15°sin9°
sin6°+cos15°sin9°/cos6°-sin15°sin9°

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