theorem Th9:
  for A,B be Subset of RLS st A c= B holds r*A c= r*B
  proof
    let A,B be Subset of RLS such that
    A1: A c=B;
    let x be object;
    assume x in r*A;
    then ex v be Element of RLS st x=r*v & v in A;
    hence thesis by A1;
  end;
