f(x)=[(sin^2x+cos^2x)^2-sin^2xcos^2x]/(2-2sinxcosx)
=(1-sinxcosx)(1+sinxcosx)/2(1-sinxcosx)
=1/2sinxcosx+1/2
=1/4sin2x+1/2
∴T=2π/2=π
∴f(x)max=1/4+1/2=3/4
∴f(x)min=-1/4+1/2=1/4