intros a nZa p; elim p; simpl in |- *; auto.
intros a0 l H' H'0 H'1; elim H'1; intros H'2 H'3; clear H'1.
cut (canonical A0 eqA ltM l);
[ intros Op0 | apply canonical_imp_canonical with (a := a0) ];
auto.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM) ltM_dec
(mults (A:=A) multA (n:=n) a
(pX
(divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) a0 (b:=a)
nZa) (pO A n)))
(mults (A:=A) multA (n:=n) a (divpf a nZa l))).
2: apply (eqp_sym _ _ _ _ _ _ _ _ _ cs n); auto.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM) ltM_dec
(mults (A:=A) multA (n:=n) a
(pX
(divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) a0 (b:=a)
nZa) (pO A n))) l).
simpl in |- *.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM) ltM_dec
(pX
(multTerm (A:=A) multA (n:=n)
(divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) a0 (b:=a)
nZa) a) (pO A n)) l).
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM) ltM_dec
(pX a0 (pO A n)) l).
change
(eqP A eqA n (pX a0 l)
(pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM) ltM_dec
(pX a0 (pO A n)) l)) in |- *; auto.
apply
(eqp_trans _ _ _ _ _ _ _ _ _ cs n)
with
(y := pX a0
(pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM)
ltM_dec (pO A n) l)).
apply (eqp_sym _ _ _ _ _ _ _ _ _ cs n); auto.
rewrite pluspf_inv1_eqa; auto.
apply canonicalp1; auto.
apply (canonical_nzeroP A A0 eqA n ltM) with (p := l); auto.
inversion H'2; auto.
auto.
auto.
Qed.

Theorem canonical_Rminus :
forall (r p q : list (Term A n)) (a : Term A n)
(nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a),
canonical A0 eqA ltM p ->
canonical A0 eqA ltM q ->
canonical A0 eqA ltM r -> canonical A0 eqA ltM (Rminus a nZa p q r).