limx→0 arctanx/x令t=arctanx原式=limt→0 t/tant=limt→0 tcost/sint=1limx→无穷[ (4+3x)/(3x-1)]^(x+1)=limx→无穷[ (1+5/(3x-1))]^(x+1)=limx→无穷[ (1+5/(3x-1))]^[(3x-1)/5*5(x+1)/(3x-1)]=limx→无穷[ (1+5/(3x-1))]^(3x-1)/5]^lim(x->∞)[5(x+1)/(3x-1)]=e^(5/3)