intros Q a b H' p q H'0 H'1.
cut (~ zeroP (A:=A) A0 eqA (n:=n) b);
[ intros nZb
| apply canonical_nzeroP with (ltM := ltM) (p := q);
apply inPolySet_imp_canonical with (L := Q) ];
auto.
cut (canonical A0 eqA ltM p);
[ intros Op0 | apply canonical_imp_canonical with (a := a) ];
auto.
cut (canonical A0 eqA ltM (pX b q));
[ intros Op1 | apply inPolySet_imp_canonical with (L := Q) ];
auto.
cut (~ zeroP (A:=A) A0 eqA (n:=n) a);
[ intros Z0 | apply canonical_nzeroP with (ltM := ltM) (p := p) ];
auto.
cut (canonical A0 eqA ltM q);
[ intros Op2 | apply canonical_imp_canonical with (a := b) ];
auto.
cut (~ zeroP (A:=A) A0 eqA (n:=n) b);
[ intros Z1 | apply canonical_nzeroP with (ltM := ltM) (p := q) ];
auto.
apply
reduceplus_eqp_com
with
(1 := cs)
(p := minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec
(mults (A:=A) multA (n:=n) b p) (mults (A:=A) multA (n:=n) a q))
(q := Rminus b nZb
(minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec
(mults (A:=A) multA (n:=n) b p)
(mults (A:=A) multA (n:=n) a q)) (pX b q)
(mults (A:=A) multA (n:=n) b p)); auto.
apply Rminus_is_reduceplus; auto.
apply divPp_mults1; auto.
intros b0 H'2; apply (canonical_imp_in_nzero A A0 eqA n ltM p); auto.
red in |- *; intros a0 H'2; apply in_minuspf_spoly_in; auto.
apply sp_Rminus; auto; auto.
Qed.

Theorem spoly_reduceplus_pO :
forall (Q : list (poly A0 eqA ltM)) (p q : list (Term A n)),
inPolySet A A0 eqA n ltM q Q ->
canonical A0 eqA ltM p ->
reduceplus A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec Q
(multpf A A0 eqA plusA multA eqA_dec n ltM ltM_dec p q)
(pO A n).