（cos7°-cos8°cos15°）/（cos23°-cos8°cos15°）=
来源：学生作业帮助网 编辑：六六作业网 时间：2024/12/19 08:52:17
（cos7°-cos8°cos15°）/（cos23°-cos8°cos15°）=（cos7°-cos8°cos15°）/（cos23°-cos8°cos15°）=（cos7°-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