intros P H p q f H0 H1 H2 H3 H4 H5.
generalize errorBoundedMultMin errorBoundedMultMax; intros H6 H7.
cut (MinOrMaxP b radix P);
[ intros | case H; intros H'1 (H'2, (H'3, H'4)); auto ].
case (H8 (p * q)%R f); auto; intros H9.
generalize (H7 (Fopp p) q (Fopp f)); intros H12.
lapply H12; auto with float; intros H10; clear H12.
lapply H10; auto; intros H12; clear H10.
lapply H12;
[ intros H10
| unfold FtoRradix in |- *; rewrite Fopp_correct; auto with real ];
clear H12.
lapply H10; auto; intros H12; clear H10.
lapply H12; [ intros H10 | simpl in |- *; auto ]; clear H12.
lapply H10; [ intros H12 | idtac ]; clear H10.
2: replace (Fopp p * q)%R with (- (p * q))%R;
[ apply MinOppMax; auto | idtac ].
2: unfold FtoRradix in |- *; rewrite Fopp_correct; auto with real.
elim H12; intros r H10; clear H12; elim H10; intros H11 H12; clear H10.
elim H12; clear H12; intros H10 H12.
exists (Fopp r); split; [ generalize H11 | split; auto with float ].
unfold FtoRradix in |- *; repeat rewrite Fopp_correct; intros H13;
rewrite H13; ring.
generalize (H6 (Fopp p) q (Fopp f)); intros H12.
lapply H12; auto with float; intros H10; clear H12.
lapply H10; auto; intros H12; clear H10.
lapply H12;
[ intros H10
| unfold FtoRradix in |- *; rewrite Fopp_correct; auto with real ];
clear H12.
lapply H10; auto; intros H12; clear H10.
lapply H12; [ intros H10 | simpl in |- *; auto ]; clear H12.
lapply H10; [ intros H12 | idtac ]; clear H10.
2: replace (Fopp p * q)%R with (- (p * q))%R;
[ apply MaxOppMin; auto | idtac ].
2: unfold FtoRradix in |- *; rewrite Fopp_correct; auto with real.
elim H12; intros r H10; clear H12; elim H10; intros H11 H12; clear H10.
elim H12; clear H12; intros H10 H12.
exists (Fopp r); split; [ generalize H11 | split; auto with float ].
unfold FtoRradix in |- *; repeat rewrite Fopp_correct; intros H13;
rewrite H13; ring.
Qed.

Theorem errorBoundedMult :
forall P,
RoundedModeP b radix P ->
forall p q f : float,
Fbounded b p ->
Fbounded b q ->
(- dExp b <= Fexp p + Fexp q)%Z ->
P (p * q)%R f ->
exists r : float,
r = (p * q - f)%R :>R /\ Fbounded b r /\ Fexp r = (Fexp p + Fexp q)%Z.