Functions count the of functions f:[m→[m one-one correspondence In] [m] [ml→[ml台[m]" l[n]→[ml=l[m]|=mn "Combinatorial proof."Functions f : [n] ￾ [m] count the # of functions one-one correspondence [n] ￾ [m] ⇥ [m] n |[n] ￾ [m]| = |[m] n| = mn “Combinatorial proof.” [n] [m]