theorem Th52:
  for A,B be Subset of RLS st A c= B holds Affin A c= Affin B
 proof
  let A,B be Subset of RLS;
  assume A1: A c=B;
  B c=Affin B by Lm7;
  then A c=Affin B by A1;
  hence thesis by Th51;
 end;
