A2:
dom (f ") = dom f
by VALUED_1:def 7;

len f = n by CARD_1:def 7;

hence len (f ") = n by A2, FINSEQ_3:29; :: according to CARD_1:def 7 :: thesis: verum

len f = n by CARD_1:def 7;

hence len (f ") = n by A2, FINSEQ_3:29; :: according to CARD_1:def 7 :: thesis: verum