theorem Th57:
  for a being object holds 1 |-> a = <*a*>
proof let a be object;
  1 in Seg 1;
  then len(1 |-> a) = 1 & (1 |-> a).1 = a by CARD_1:def 7,FUNCOP_1:7;
  hence thesis by FINSEQ_1:40;
end;
