奇妙的证明 —— 0! = 1(a^0=1) 1. 0!=1 (n−1)!=n!n(n−1)!=n!n 则: 0!=1!1=10!=1!1=1 2. a^0=1 an−1=anaan−1=ana 则: a0=a1a=1a0=a1a=1