Section Pdigit.
(* n is the base *)
Variable n : Z.
(* and it is greater or equal to 2 *)
Hypothesis nMoreThan1 : (1 < n)%Z.
Let nMoreThanOne := Zlt_1_O _ (Zlt_le_weak _ _ nMoreThan1).
Hint Resolve nMoreThanOne: zarith.
intros q; elim q; simpl in |- *;
auto with zarith.
Qed.
Hint Resolve Zpower_nat_less: zarith.
intros p; rewrite <- (Zmult_1_l (Zpower_nat n p)); replace (S p) with (1 + p);
[ rewrite Zpower_nat_is_exp | auto with zarith ].
rewrite Zpower_nat_1; auto with zarith.
apply Zmult_gt_0_lt_compat_r; auto with zarith.
apply Z.lt_gt; auto with zarith.
Qed.

Theorem Zpower_nat_monotone_lt :
forall p q : nat, p < q -> (Zpower_nat n p < Zpower_nat n q)%Z.