intros x; case x; simpl in |- *; auto.
intros a l; case a; simpl in |- *; auto.
Qed.

(* Specifications: *)
Theorem divA_nZ :
forall a b : A,
~ eqA b A0 -> forall nZa : ~ eqA a A0, ~ eqA (divA b a nZa) A0.