reserve V for set;

theorem Th33:
  for M being PseudoMetricSpace, V,Q being Element of M-neighbour
   ex v being Real st V,Q is_dst v
proof
  let M be PseudoMetricSpace, V,Q be Element of M-neighbour;
  consider p being Element of M such that
A1: V=p-neighbour by Th15;
  consider q being Element of M such that
A2: Q=q-neighbour by Th15;
A3: q in Q by A2,Th4;
  p in V by A1,Th4;
  then V,Q is_dst (dist(p,q)) by A3,Th21;
  hence thesis;
end;
