来自傅健的问题
求值.(cos15°*sin9°+sin6°)/(sin15°*sin9°-cos6°)
求值.
(cos15°*sin9°+sin6°)/(sin15°*sin9°-cos6°)
1回答
2020-04-10 09:17
求值.(cos15°*sin9°+sin6°)/(sin15°*sin9°-cos6°)
求值.
(cos15°*sin9°+sin6°)/(sin15°*sin9°-cos6°)
(cos15°sin9°+sin6°)/(sin15°sin9°-cos6°)
=[cos15sin9+sin(15-9)]/[sin15sin9-(cos15-9)]
=(cos15sin9+sin15cos9-cos15sin9)/(sin15sin9-cos15cos9-sin15sin9)
=(sin15cos9)/(-cos15cos9)
=-tan15
=-sin30/(1+cos30)=根号3-2.