负的三分之14派的余弦值是多少
问题描述：
负的三分之14派的余弦值是多少
答
cos(-14π/3)
=cos(14π/3)
=cos(4π+2π/3)
=cos(2π/3)
=-coscos(π/3)
=-cos60°
=-sin30°
=-1/2