case (Z_zerop (Fnum p)).
case p; intros Fnum1 Fexp1 H'; unfold FtoRradix, FtoR in |- *; rewrite H';
simpl in |- *; auto with real.
apply trans_eq with 0%R; auto with real.
intros H'; unfold FtoRradix in |- *; apply FshiftCorrect; auto.
Qed.

Theorem Fnormalize_Fopp :
forall p : float, Fnormalize (Fopp p) = Fopp (Fnormalize p).