怎么算cos-32π/3

问题描述:

怎么算cos-32π/3

解cos(-32π/3)
=cos32π/3
=cos(10π+2π/3)
=cos(2π/3)
=cos(π-π/3)
=-cosπ/3
=-1/2.为什么cos-32π/3=cos32π/3?这是余弦公式
cos(-a)=cosa非常感谢