极限，n趋向于无穷大，lim{n[In(n+2)-Inn]}；求极限，n趋向于无穷大,lim根号下n乘以sin(pai/n);lim{n[In(n+2)-Inn]}=lim{n[In（1

lim{n[In(n+2)-Inn]}=lim{n[In（1+2/n)]}=lim{n*(2/n)}=2，当s趋向于无穷小时，sin（x）/x=1，同理，n趋向于无穷大，(pai/n)趋向于无穷小，则lim根号下pai*[sin(pai/n)/(pai/n)]=根号下pai

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