
theorem
  N_CC = SugenoNegation 0
  proof
    set f = N_CC, g = SugenoNegation 0;
    for x being object st x in [.0,1.] holds f.x = g.x
    proof
      let x be object;
      assume x in [.0,1.]; then
      reconsider xx = x as Element of [.0,1.];
      g.xx = (1 - xx) / (1 + 0 * xx) by DefSugeno
          .= f.xx by NDef;
      hence thesis;
    end;
    hence thesis by FUNCT_2:12;
  end;
