f(x)=(1+tanx)(1-sin2x+cos2x)+3=[1+(sinx/cosx)][1-2sinxcosx+2cos²x-1]+3=[2cosx(cosx-sinx)(sinx+cosx)/cosx]+3=2cos2x+3.∴f(x)=2cos2x+3.∵-1≤cos2x≤1.∴1≤2cos2x+3≤5.即值域为[1,5].显然T=π....