reserve n   for Nat,
        r,s for Real,
        x,y for Element of REAL n,
        p,q for Point of TOP-REAL n,
        e   for Point of Euclid n;

theorem Th5:
  for D being non empty set, D1 being non empty Subset of D holds
  n-tuples_on D1 c= n-tuples_on D
  proof
    let D be non empty set, D1 be non empty Subset of D;
    n-tuples_on D /\ n-tuples_on D1 = n-tuples_on D1 by MARGREL1:21;
    hence thesis by XBOOLE_1:17;
  end;
