
theorem Th15:
  for I being non empty set for P being ManySortedSet of I for i
  being Element of I holds {P}.i is 1-element
proof
  let I being non empty set;
  let P be ManySortedSet of I;
  let i be Element of I;
  {P}.i = {P.i} by PZFMISC1:def 1;
  hence thesis;
end;
