Definition maj_Reste_E (x y:R) (N:nat) : R :=
  4 *
  (Rmax 1 (Rmax (Rabs x) (Rabs y)) ^ (2 * N) /
    Rsqr (INR (fact (Nat.div2 (pred N))))).

Lemma exp_plus : forall x y:R, exp (x + y) = exp x * exp y.