theorem
  for R being finite Approximation_Space
  for A, B being Subset of R holds
    (MarczewskiDistance R).(A,B) = (delta_1 R).(A,B)
  proof
    let R be finite Approximation_Space;
    let A, B be Subset of R;
    (MarczewskiDistance R).(A,B) = card (A \+\ B) / card (A \/ B) by Similar2;
    hence thesis by For191;
  end;
