reserve X for non empty BCIStr_1;
reserve d for Element of X;
reserve n,m,k for Nat;
reserve f for sequence of  the carrier of X;

theorem Th22:
  for X being BCI-Algebra_with_Condition(S) holds for x being
  Element of X holds x |^ 2 = x * x
proof
  let X be BCI-Algebra_with_Condition(S);
  let x be Element of X;
  thus x |^ 2 = x |^ (1 + 1) .=(x |^ 1) * x by Def6
    .= x*x by Th21;
end;
