intros b z p H'; elim H'; intros r E; elim E; intros H'0 H'1; elim H'1;
intros H'2 H'3; clear H'1 E H'.
exists (Fopp r); split; auto.
rewrite <- (Ropp_involutive p).
rewrite <- H'0; auto.
unfold FtoRradix in |- *; apply Fopp_correct; auto.
split.
apply oppBounded; auto.
simpl in |- *; auto.
Qed.

Theorem absFBounded :
forall (b : Fbound) (f : float), Fbounded b f -> Fbounded b (Fabs f).