proposition: Lemma exp_not0 : forall a : Z, a <> 0%Z -> forall m : nat, Exp a m <> 0%Z.
proof: Proof. intros a Ha. simple induction m. simpl in |- *. discriminate. intros n IH. simpl in |- *. intro. elim (Zmult_ab0a0b0 a (Exp a n)). assumption. assumption. assumption. Qed.
imports: ZArith lemmas natZ