0 < n^n/(2n!) < (1/n!){n^n/(n+1)(n+2)...(2n)} < 1/n!∴由夹逼定理,lim（n->∞）n^n/(2n!) = 00 < n!/n^n < (1*2*3*...*n)/[n*n*n*...*n] < 1/n∴由夹逼定理,lim（n->∞）n!/n^n = 0