sin(α+π/6)=cos(π/2-(α+π/6))=cos(π/3-a)=1/3 sin(π/6-α/2) =±√{[1-cos(2(π/6-α/2))]/2} =±√{[1-cos(π/3-α)]/2} =±√{[1-1/3]/2} =[±√3]/3
