1-Sin(α/2+3π)-Cos2α/4=Sin2α/4

1-sin(α/2+3*pi)-cos^2(α/4)=sin^2(α/4)

1+sin(α/2)-cos^2(α/4)-sin^2(α/4)=0

1+sin(α/2)-(cos^2(α/4)+sin^2(α/4))=0

1+sin(α/2)-1=0

sin(α/2)=0

α/2=pi*n

α=2*pi*n