intros a b c; case a; case b; case c; simpl in |- *; auto.
intros a0 m a1 m0 a2 m1 nZc H' H'0 H'1; split; auto.
case H'1; intros H'3 H'4; clear H'1.
case H'0; intros H'2 H'5; clear H'0.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with
(y := divA
(plusA (multA (divA a2 a0 nZc) a0) (multA (divA a1 a0 nZc) a0))
a0 nZc); auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with
(y := divA (multA (plusA (divA a2 a0 nZc) (divA a1 a0 nZc)) a0) a0 nZc);
auto.
apply divA_eqA_comp with (1 := cs); auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with (y := plusA (multA a0 (divA a2 a0 nZc)) (multA a0 (divA a1 a0 nZc)));
auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with (y := multA a0 (plusA (divA a2 a0 nZc) (divA a1 a0 nZc)));
auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with
(y := multA (plusA (divA a2 a0 nZc) (divA a1 a0 nZc)) (divA a0 a0 nZc));
auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with
(y := divA (multA a0 (plusA (divA a2 a0 nZc) (divA a1 a0 nZc))) a0 nZc);
auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with
(y := multA (divA a0 a0 nZc) (plusA (divA a2 a0 nZc) (divA a1 a0 nZc)));
auto.
apply divA_multA_comp_r with (1 := cs); auto.
apply
(eqA_trans _ _ _ _ _ _ _ _ _ cs)
with (y := multA (plusA (divA a2 a0 nZc) (divA a1 a0 nZc)) A1);
auto.
apply (eqA_sym _ _ _ _ _ _ _ _ _ cs); auto.
apply multA_eqA_comp with (1 := cs); auto.
apply (eqA_sym _ _ _ _ _ _ _ _ _ cs); auto.
apply divA_A1 with (1 := cs); auto.
apply multA_A1_r with (1 := cs); auto.
Qed.

Theorem divTerm_invTerm_l :
forall (a b : Term A n) (nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a),
eqTerm (A:=A) eqA (n:=n) b (multTerm (A:=A) multA (n:=n) (divTerm b nZa) a) ->
eqTerm (A:=A) eqA (n:=n) (divTerm (invTerm (A:=A) invA (n:=n) b) nZa)
(invTerm (A:=A) invA (n:=n) (divTerm b nZa)).