lim(x→无穷)xsin(2x/(1+x^2))
=lim(x→无穷)xsin[(2/x)/(1/x^2 +1)]
=lim(1/x→0)x[(2/x)/(1/x^2 +1)]
=lim(1/x→0)[2/(1/x^2 +1)]
=2/1=2答案也有可能错误啊