(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/02 05:14:50
![(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=](/uploads/image/z/3712519-55-9.jpg?t=%EF%BC%88cos7%C2%B0-cos8%C2%B0cos15%C2%B0%EF%BC%89%2F%EF%BC%88cos23%C2%B0-cos8%C2%B0cos15%C2%B0%EF%BC%89%3D)
(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=
(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=
(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=
cos7°=cos(15°-8°)=cos8°cos15°+sin8°sin15°,那么cos7°-cos8°cos15°=sin8°sin15°;
cos23°=cos(8°+15°)=cos8°cos15°-sin8°sin15°,那么cos23°-cos8°cos15°=-sin8°sin15°
所以原式=(sin8°sin15°)/(-sin8°sin15°)=-1