cos(50π/3)=cos(16π+2π/3)=cos(2π/3)=-1/2

1/2

就是扣塞六十度,二分之一

cos(2π/3) =-1/2.分析过程如下:π-α与α的三角函数值之间的关系:(1)sin(π-α)=sinα (2)cos(π-α)=-cosα (3)tan(π-α)=-tanα (4)cot(π-α)=-cotα 根据公式(3)可得:cos(2π/3) =cos(π-π/3) =-cosπ/3,而cosπ/3=cos60°=sin30°=1/2.所以cos(2π/3)

解答:cos2π/3=-1/2

cos(5π/3)=cos(2π-π/3)=cos(-π/3)=cos(π/3)=1/2

cos3分之4π=cos-3分之2π=-1/2 【精】【锐】

解cos15π/3=cos5π=cosπ=-1

你好!cos(16兀/3)=cos(16兀/3-6π)=cos(-2π/3)=-cos(π-2π/3)=-cosπ/3=-1/2如果对你有帮助,望采纳.

解: cos(-16π/3)=cos(16π/3)=cos(5π+π/3)=-cos(π/3)=-1/2 (选C) 祝你开心