intuition.
unfold leRat, bleRat, ratCD, rat1 in *.
unfold natToPosnat, posnatToNat in *.
destruct d.
rewrite mult_1_r in H.
rewrite mult_1_l in H.
destruct (le_gt_dec n x); intuition.
discriminate.
Qed.

Theorem ratFraction_le_1 :
forall r1 r2,
r1 <= r2 ->
r1 * (ratInverse r2) <= 1.