reserve E, x, y, X for set;
reserve A, B, C for Subset of E^omega;
reserve a, a1, a2, b for Element of E^omega;
reserve i, k, l, m, n for Nat;

theorem
  A ^^ A c= A+
proof
  A ^^ A = A |^ 2 by FLANG_1:26;
  hence thesis by Th49;
end;
