intuition.
destruct (eq_Rat_dec r1 0); intuition.
destruct (eq_Rat_dec r2 0); intuition.
exfalso.
eapply H.
apply ratAdd_0; eauto.
apply H1.
specialize (ratAdd_0 r1 r2); intuition.
apply H1.
specialize (ratAdd_0 r1 r2); intuition.
Qed.

Theorem rat_num_0 : forall d,
(RatIntro O d) == 0.