(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=

来源:学生作业帮助网 编辑:作业帮 时间:2024/03/28 23:41:58
(cos7°-cos8°cos15°)/(cos23°-cos8°cos15°)=

(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