intuition.
destruct d.
assert (1 <= n)%nat.
destruct n.
exfalso.
eapply H.
eapply rat_num_0.
omega.
exists p.
rewrite expRat_terms.
eapply leRat_trans.
2:{
eapply leRat_terms.
eapply H0.
eapply le_refl.
}
erewrite expnat_1.
eapply leRat_terms.
intuition.
edestruct p.
unfold natToPosnat, posnatToNat.
eapply le_expnat_2.
Grab Existential Variables.
eapply expnat_nz.
econstructor.
destruct p.
econstructor.
intuition.
Qed.

Lemma expRat_1 : forall n,
expRat 1 n == 1.