cos10°cos110°-cos200°cos100°?

分类: 作业答案 • 2022-06-07 12:50:43

问题描述：

答

cos10°cos110°-cos200°cos100°
=cos10°cos110°-cos(90+110)°cos(90+10)°
=cos10°cos110°-sin110°sin10°
=cos(10+110)°
=cos120°
=-1/2