intuition.
destruct (eq_Rat_dec r2 0).
rewrite e.
eapply rat0_le_all.
eapply (@leRat_ratMult_same_r (ratInverse r2)).
intuition.
eapply ratInverse_nz.
eauto.
rewrite ratMult_comm.
rewrite ratInverse_prod_1.
intuition.
intuition.
Qed.

Theorem eqRat_refl_eq :
forall x y,
x = y ->
x == y.