lim tanx^2/1-cosx=lim (sinx^2/cosx^2)/(1-cosx)=lim (sinx^2)/[cosx^2*(1-cosx)]=lim (1-cosx^2)/[cosx^2*(1-cosx)]=lim [(1+cosx)(1-cosx)]/[cosx^2*(1-cosx)]
分子分母同时约掉(1-cosx)
=lim (1+cosx)/cosx^2=2
祝学习进步~