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

theorem Th93:
  (A?) ^^ (A?) = A |^ (0, 2)
proof
  A? = A |^ (0, 1) by Th79;
  then (A?) ^^ (A?) = A |^ (0 + 0, 1 + 1) by Th37;
  hence thesis;
end;
