theorem Th16:
  Int T c= T
proof
  let x be object;
  assume
A1: x in Int T;
  then reconsider x99= x as Point of GX;
  T` c= Cl T` by PRE_TOPC:18;
  then not x99 in T` by A1,XBOOLE_0:def 5;
  hence thesis by A1,XBOOLE_0:def 5;
end;
