
theorem Th2:
  for T1 being non empty 1-sorted, T2 being 1-sorted, S being
  sequence of T1 st rng S c= the carrier of T2 holds S is sequence of T2
proof
  let T1 be non empty 1-sorted, T2 be 1-sorted, S be sequence of T1;
A1: dom S = NAT by FUNCT_2:def 1;
  assume rng S c= the carrier of T2;
  hence thesis by A1,FUNCT_2:2;
end;
