Hint Resolve scal_hom.
(* Get homogeneity part *)
Fixpoint get_hom (n m : nat) {struct n} : vect n -> vect n :=
match n return (vect n -> vect n) with
| 0%nat => fun a => match m with O => a | S _ => 0 end
| S n1 =>
fun l1 =>
let (l2, l3) := l1 in
((match m with O => [0]
| S m1 => get_hom n1 m1 l2
end), get_hom n1 m l3)
end.

Lemma sumEr n f m : sum n f m.+1 = f m.+1 + sum n f m.