作业帮化简COS8°-SIN17°SIN9°/COS9°
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/06 09:09:55
化简COS8°-SIN17°SIN9°/COS9°
化简COS8°-SIN17°SIN9°/COS9°
化简COS8°-SIN17°SIN9°/COS9°
∵cos8°=cos(17°-9°)=cos17°cos9°+sin17°sin9°
∴cos8°-sin17°sin9°=cos17°cos9°
∴(cos8°-sin17°sin9°)/cos9°=cos17°cos9°/cos9°=cos17°
最后答案为：cos17°
COS8°-SIN17°SIN9°/COS9°=（COS8°+cos26°/2-cos8°/2）/cos9°=（cos26°/2+cos8°/2）cos9°
=cos17°*cos9°/cos9°=cos17°