C=1/16
(一下都是x趋近于无穷大)
lim[ln(1+ce^x)/√(1+cx^2)]
=lim[ln(ce^x)/√(cx^2)]
=lim[(lnc+x)/(x*√c)]
=lim[lnc/(x*√c)+1/√c]=1/√c
解1/√c=4就得C=1/16