rattac.
inversion H; clear H; subst.
inversion H0; clear H0; subst.
simpl.
arithNormalize.
repeat rewrite mult_0_r.
repeat rewrite plus_0_r.
trivial.
Qed.

Lemma ratMult_small_le : forall r1 r2,
r2 <= 1 ->
r1 * r2 <= r1.