见图
解如下图所示
x->∞ln(1+1/x) = 1/x +o(1/x)arccotx=arctan(1/x) = 1/x +o(1/x)lim(x->+∞) ln(1+1/x) /arccotx=lim(x->+∞) (1/x) / (1/x)=1
