Sin(π÷6-α)=a,求cos(2π/3-α)

问题描述:

Sin(π÷6-α)=a,求cos(2π/3-α)

因为cos(π/2+α) =-Sin(π/+α)
cos(2π/3-α) =cos[π/2+(π/6-α)]
=-Sin(π/6-α)=-a