unfold Ravg.
simpl.
unfold Rdiv.
rewrite Rmult_0_l...
Qed.

(* Specifications: *)
Lemma Ravg_one h: Ravg (h :: nil) = h.
Instance Ravg_Permutation: Proper (Permutation ==> eq) Ravg.
Lemma Ravg_0_le l: (forall x, In x l -> 0 <= x) -> 0 <= Ravg l.
Proof with auto with real.