Definition RInt_val (f : R -> V) (a b : R) (n : nat) :=
  Riemann_sum f (SF_seq_f2 (fun x y => (x + y) / 2) (unif_part a b n)).

Lemma RInt_val_ext (f g : R -> V) (a b : R) (n : nat) : (forall x, Rmin a b <= x <= Rmax a b -> f x = g x) -> RInt_val g a b n = RInt_val f a b n.