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_swap : forall (f : R -> V) (a b : R) (n : nat), RInt_val f a b n = opp (RInt_val f b a n).