theorem Th93:
  for HPS being satisfying_euclidean Heptatonic_Pythagorean_Score
  for f1,f2 being Element of HPS
  holds intrval(f1,f2) = (the Ratio of HPS).(f1,f2)
  proof
    let HPS be satisfying_euclidean Heptatonic_Pythagorean_Score;
    let f1,f2 be Element of HPS;
    (the Ratio of HPS).(f1,f2) = @f2 / @f1 by Def25;
    hence thesis by Def21;
  end;
