reserve E, x, y, X for set;
reserve A, B, C, D for Subset of E^omega;
reserve a, a1, a2, b, c, c1, c2, d, ab, bc for Element of E^omega;
reserve e for Element of E;
reserve i, j, k, l, n, n1, n2, m for Nat;

theorem Th24:
  A |^ 0 = {<%>E}
proof
  ex concat being sequence of  bool (E^omega) st A |^ 0 = concat.0 &
  concat.0 = {<%>E} & for i holds concat.(i + 1) = concat.i ^^ A by Def2;
  hence thesis;
end;
