求值:(sin9°+sin6°cos15°)/(cos9°-sin6°sin15°)
问题描述：
求值:(sin9°+sin6°cos15°)/(cos9°-sin6°sin15°)
怎么做?
过程!
答
sin9+sin6cos15
=sin(15-6)+sin6cos15
=sin15cos6-sin6cos15+sin6cos15
=sin15cos6
cos9-sin6sin15
=cos(15-6)-sin6sin15
=cos15cos6+sin15sin6-sin6sin15
=cos15cos6
sin15cos6/cos15cos6
=tan15