
theorem
  for t being BinOp of [.0,1.] holds
    conorm conorm t = t
  proof
    let t be BinOp of [.0,1.];
    set tt = conorm conorm t;
    for a,b being Element of [.0,1.] holds
      t.(a,b) = tt.(a,b)
    proof
      let a, b be Element of [.0,1.];
A1:   1 - a in [.0,1.] & 1 - b in [.0,1.] by OpIn01;
      tt.(a,b) = 1 - (conorm t).(1-a,1-b) by CoDef
         .= 1 - (1 - t.(1-(1-a),1-(1-b))) by CoDef,A1;
      hence thesis;
    end;
    hence thesis by BINOP_1:2;
  end;
