reserve MS for satisfying_equiv MusicStruct;
reserve a,b,c,d,e,f for Element of MS;
reserve MS for satisfying_octave_descendent_constructible
  classical_octave satisfying_octave_constructible classical_fifth
  satisfying_fifth_constructible satisfying_harmonic_closed satisfying_Nat
  satisfying_commutativity satisfying_interval satisfying_equiv satisfying_Real
  non empty MusicStruct,
  fondamentale,frequency for Element of MS;

theorem Th62:
  @(spiral_of_fifths(MS,frequency,frequency).2) /
  @frequency = (3 * 3 qua Real) / (2 * 2 * 2)
  proof
    @(spiral_of_fifths(MS,frequency,frequency).2) /
    @frequency = ((9 qua Real) / 8 * @frequency) / @frequency by Th59
              .= (3 * 3 qua Real) / (2 * 2 * 2) by XCMPLX_1:89;
    hence thesis;
  end;
