已知sin(π/6-a)=根号3/3,则 cos(4π/3+a)

问题描述:

已知sin(π/6-a)=根号3/3,则 cos(4π/3+a)


cos(4π/3+a)
=cos(π+π/3+a)
=-cos(π/3+a)
=-cos[π/2-(π/6-a)]
=-sin(π/6-a)
=-√3/3