theorem
  c_n(r).(n+2) / c_d(r).(n+2) = (scf(r).(n+2) * c_n(r).(n+1) + c_n(r).n)
  / (scf(r).(n+2) * c_d(r).(n+1) + c_d(r).n)
proof
  c_n(r).(n+2) = scf(r).(n+2) * c_n(r).(n+1) + c_n(r).n by Def5;
  hence thesis by Def6;
end;
