1.sin(-16Π/3)=sin(-6Π2/3×Π)=sin(2/3×Π)=√3/22.cos(-945°）=cos(-1080°135°)=cos(135°)=-√2/23.cos(πα）=-cosα=-1/2cosα=1/2sina=√1-(1/2)=±√3/2sin(-α)=±√3/24.1/2sin2x√3/2cos2x-√3/2=sin(2xΠ/6)-√3/2(1).f(25π/6)=sin(50Π/6Π/6)-√3/2=sin(48Π/63Π/6)-√3/2=1-√3/2(2).f(α/2)=1/4-√3/2f(α/2)=sin(αΠ/6)-√3/2=1/4-√3/2说明sin(αΠ/6)=1/4sinαcosΠ/6cosαsinΠ/6=√3/2sinα1/2cosα=1/4√3sinαcosα=1/2sinαcosα=1联立上面两式得sinα=(√3±√15)/8因为α属于（0,π),则sinα>0,所以sinα=(√3√15)/8