题目内容：

1.sin(-27π/4)得正弦数值 2.cos(-79π/6)的余弦值 3.cos31π/6的余弦值

优质解答

sin(-27π/4)=sin(-3π/4)=-sin(3π/4)=-sin(π/4)=-√2/2
cos(-79π/6)=cos(4π/6)=-cos(π/3)=-1/2
cos31π/6=cos5π/6=-cosπ/6=-√3/2