lim(x-->∞)x/(x²+1)=lim(x-->∞)(1/x)/(1+1/x²)=0/(1+0)=0令t=x/(x²+1)那么x-->∞,t-->0lim(x-->∞)sin（x/x^2+1)/(x/x^2+1)=lim(t-->0)(sint)/t=1
