
theorem Th18:
  for T being non empty TopSpace, p being Point of T holds p
  is_dense_point_of Cl{p}
proof
  let T be non empty TopSpace, p be Point of T;
  {p} c= Cl{p} & p in {p} by PRE_TOPC:18,TARSKI:def 1;
  hence p in Cl{p};
  thus thesis;
end;
