
theorem Th16:
  for f1,f2 being complex-valued Function holds dom (f1/"f2) = dom
  f1 /\ dom f2
proof
  let f1,f2 be complex-valued Function;
  thus dom (f1/"f2) = dom f1 /\ dom (f2") by Def4
    .= dom f1 /\ dom f2 by Def7;
end;
