proposition: Lemma or5_equiv: forall A1 A2 A3 A4 A5 , or5 A1 A2 A3 A4 A5 <-> A1 \/ A2 \/ A3 \/ A4 \/ A5 .
proof: Proof. intros. split. intros H. rewrite <- or4_equiv. destruct H. constructor 1. exact H. constructor 2. exact H. constructor 3. exact H. constructor 4. left. exact H. constructor 4. right. exact H. intros H. destruct H. constructor 1. exact H. rewrite <- or4_equiv in H. destruct H. constructor 2. exact H. constructor 3. exact H. constructor 4. exact H. constructor 5. exact H. Qed.
imports: Coq(Setoid Morphisms)