proposition: Lemma Re_wd : forall c c' : CC, c [=] c' -> Re c [=] Re c'.
proof: Proof. intros c c'. elim c. intros x y. elim c'. intros x' y'. simpl in |- *. unfold cc_eq in |- *. simpl in |- *. intros. elim H. auto. Qed.
imports: CoRN.reals.NRootIR