lim(x→0)ln(1+x^2)=0
y=ln(1+x^2)>0
y=ln(1+x^2)渐近线是y=0 lim(x→0)ln(1+x^2)=0
y=ln(1+x^2)>0
y=ln(1+x^2)渐近线是y=0