theorem Th16:
  for n being Nat
  for r being positive Real
  for a being Point of TOP-REAL n holds a in Ball(a,r)
proof let n be Nat;
  let r be positive Real;
  let a be Point of TOP-REAL n;
  |. a-a .| = 0 by TOPRNS_1:28;
  hence thesis by TOPREAL9:7;
end;
