proposition: Lemma C0_neq_R0_neq : forall z, z <> 0 <-> (Cre z <> 0%R \/ Cim z <> 0%R).
proof: Proof. intro z ; split ; intro H. destruct z as (a,b) ; case (Req_or_neq a) ; case (Req_or_neq b) ; intros Ha Hb. elim H ; rewrite Ha, Hb ; reflexivity. right ; intuition. left ; intuition. left ; intuition. intro Hf ; destruct H ; apply H ; rewrite Hf ; intuition. Qed.
imports: Cdefinitions