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 Th7:
  x in A & x <> <%>E & n > 0 implies A |^ n <> {<%>E}
proof
  assume that
A1: x in A & x <> <%>E and
A2: n > 0;
  A <> {<%>E} by A1,TARSKI:def 1;
  hence thesis by A2,FLANG_1:29;
end;
