Hint Resolve mul_add_br_add_br : Recurrence.
Hint Rewrite @mul_add_br_add_br : Recurrence.

(* Lemma 14 *)
Lemma mul_mul_br_mul_br: forall `{Ring R} (n: nat)
(r1 r2: R) (f1 f2: nat -> R),
({{r1, mult, f1}} # n) * ({{r2, mult, f2}} # n) =
((mkBR (r1 * r2) mult (fun n => (f1 n * f2 n))) # n).