f(x)= - √3sin(2x)+sinxcosx
f(α/2)= - √3sinα+sin(α/2)cos(α/2)=-√3sinα+1/2sinα=2sinα(-√3/2+1/4)
又f(α/2)=1/4-(√3)/2=-√3/2+1/4 ∴2sinα=1,sinα=1/2