intuition.
eapply getSupport_In_evalDist.
intuition.
rewrite H in H1.
clear H.
unfold marginal_l in *.
simpl in *.
eapply sumList_0 in H1; eauto.
eapply ratMult_0 in H1.
intuition.
eapply getSupport_In_evalDist;
eauto.
dist_compute.
Qed.

Theorem in_support_marginal_r :
forall (A B : Set){eqd: EqDec B}(c1 : Comp (A * B))(c2 : Comp B),
(forall b, evalDist c2 b == marginal_r c1 b) ->
forall p,
In p (getSupport c1) ->
In (snd p) (getSupport c2).