intros P a b H'; elim H'; auto.
intros P0 a0 b0 H'0;
cut
(red A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec
(spolyp A A0 A1 eqA plusA invA minusA multA divA cs eqA_dec n ltM
ltM_dec os b0 a0) P0); auto.
case a0; case b0; unfold red in |- *; simpl in |- *; auto.
intros x H'1 x0 H'2 H'3; inversion H'3.
apply Spoly_10 with (Cp := H'2) (Cq := H'1); auto.
apply red_com; auto.
intros P0 a0 b0 c.
case c; case b0; case a0; simpl in |- *.
intros x; case x; simpl in |- *; auto.
intros c0 x0 c1 x1 c2 H'0 H'1 H'2 H'3 H'4 H'5; elim H'5.
intros a1 l c0 x0; case x0; simpl in |- *.
intros c1 x1 c2 H'0 H'1 H'2 H'3 H'4 H'5; elim H'5.
intros a2 l0 c1 x1; case x1; simpl in |- *.
intros c2 H'0 H'1 H'2 H'3 H'4 H'5; elim H'5.
intros a3 l1 c2 H'0 H'1 H'2 H'3 H'4 H'5.
change
(Spoly_1 A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec P0
(pX a1 l) (pX a2 l0)) in |- *.
apply Spoly_11 with (d := a3) (t := l1); auto.
change
(inPolySet A A0 eqA n ltM
(s2p A A0 eqA n ltM (mks A A0 eqA n ltM (pX a3 l1) c2)) P0)
in |- *.
apply in_inPolySet; simpl in |- *; auto.
red in |- *; intros H; inversion H.
Qed.

Theorem imp_in :
forall (P : list (poly A0 eqA ltM)) (a : list (Term A n)),
inPolySet A A0 eqA n ltM a P ->
exists b : poly A0 eqA ltM, In b P /\ a = s2p A A0 eqA n ltM b.