
theorem Th32:
  for I being non degenerated domRing-like commutative Ring for u
being Element of the_Field_of_Quotients(I) holds (quotaddinv(I)).(u) is Element
  of the_Field_of_Quotients(I)
proof
  let I be non degenerated domRing-like commutative Ring;
  let u be Element of the_Field_of_Quotients(I);
  reconsider s = u as Element of Quot.I;
  (quotaddinv(I)).(u) = qaddinv(s) by Def14;
  hence thesis;
end;
