因为A=e^LnA,（A大于0）所以 sec^2 x=e^Lnsec^2 xlim(sec^2 x)^cot^2 x = lim e^Lnsec^2 x x趋近于0 x趋近于0又因为 lim sec^2 x =lim（1+tan^2x）=1x趋近于0 x趋近于0所以,lim Lnsec^2 x =0 x趋近于0lim e^Lnsec^2 ...