y=sin²(x/2)-sin(x/2)cos(x/2)
=(1-cosx)/2-(1/2)sinx
=1-(1/2)(sinx+cosx)
=1-(√2/2)sin(x+π/4)
当sin(x+π/4)=-1时,y有最大值,y(max)=1+√2/2；
当sin(x+π/4)=1时,y有最小值,y(min)=1-√2/2；
y=sin²(x/2)-sin(x/2)cos(x/2)
=(1-cosx)/2-(1/2)sinx
=1-(1/2)(sinx+cosx)
=1-(√2/2)sin(x+π/4)
当sin(x+π/4)=-1时,y有最大值,y(max)=1+√2/2；
当sin(x+π/4)=1时,y有最小值,y(min)=1-√2/2；