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
  (A |^ (1, n))? = A |^ (0, n)
proof
  thus (A |^ (1, n))? = {<%>E} \/ (A |^ (1, n)) by Th76
    .= A |^ (0, 0) \/ (A |^ (0 + 1, n)) by Th45
    .= A |^ (0, n) by Th25;
end;
