theorem Th28:
  for S, T being non empty TopSpace, f being Function of S, T, A
  being dense Subset of T st f is being_homeomorphism holds f"A is dense
proof
  let S, T be non empty TopSpace, f be Function of S, T, A be dense Subset of
  T such that
A1: f is being_homeomorphism;
A2: Cl A = [#]T by TOPS_1:def 3;
  thus Cl (f"A) = f"(Cl A) by A1,TOPS_2:59
    .= [#]S by A2,TOPS_2:41;
end;
