计算值 COS(-2040°)

问题描述:

计算值 COS(-2040°)

=cos(-60°)
=cos60°
=1/2

COS(-2040°)
=cos(2160-2040)
=cos120
=-cos60
=-0.5

=cos2040
-=cos(360×5+240)
=cos240
=cos(180+60)
=-cos60
=-1/2