intros a b; case a; case b; simpl in |- *; auto.
split; auto.
apply divA_is_multA with (1 := cs); auto.
Qed.
Set Implicit Arguments.
Unset Strict Implicit.
Definition ppc : Term A n -> Term A n -> Term A n.
intros H; case H; intros b2 c2 H'; case H'; intros b3 c3; simpl in |- *;
exact (A1, ppcm_mon n c2 c3).
Defined.
Set Strict Implicit.
Unset Implicit Arguments.

Theorem ppc_com :
forall a b : Term A n, eqTerm (A:=A) eqA (n:=n) (ppc a b) (ppc b a).