reserve a, b, k, n, m for Nat,
  i for Integer,
  r for Real,
  p for Rational,
  c for Complex,
  x for object,
  f for Function;
reserve l, n1, n2 for Nat;
reserve s1, s2 for Real_Sequence;

theorem
  c_d(r).(n+2) >= scf(r).(n+2) * c_d(r).(n+1)
proof
  set s=scf(r);
  set s1=c_d(r);
  set m=s.(n+2)*s1.(n+1);
  s1.(n+2)-s.(n+2)*s1.(n+1)=s.(n+2)*s1.(n+1)+s1.n-s.(n+2)*s1.(n+1) by Def6;
  then s1.(n+2)-s.(n+2)*s1.(n+1)>=0 by Th51;
  then s1.(n+2)-m+m>=0+m by XREAL_1:6;
  hence thesis;
end;
