sinα+cosα=√3/3(sinα+cosα)^2=1/32sinacosa=1/3-1=-2/3sinα-cosα>0,(sinα-cosα)^2=1-2sinacosa=5/3sinα-cosα=√(5/3)cos2α=-(sinα-cosα))(sinα+cosα)=-√(5/3) * (√3/3)=-(√5)/3