reserve i,j,k for Nat;

theorem Th3:
  for K being commutative non empty multMagma holds
    the multF of K is commutative
proof
  let K be commutative non empty multMagma;
  now
    let a,b be Element of K;
    thus (the multF of K).(a,b)=a*b .= b*a
      .=(the multF of K).(b,a);
  end;
  hence thesis by BINOP_1:def 2;
end;
