intros e n m H' H'0.
case (Zle_or_lt n m); auto; intros Z1.
absurd (powerRZ e n <= powerRZ e m)%R; auto.
apply Rlt_not_le.
apply Rlt_powerRZ; auto.
Qed.

Theorem Rinv_powerRZ :
forall (e : R) (n : Z), e <> 0%R -> (/ powerRZ e n)%R = powerRZ e (- n).