proposition: Lemma Cantor_omega_pr2: cardinal Cantor_Omega = aleph_one.
proof: Proof. move: CIS_omega => h. move: (cnext_pr1 (proj1 h)); rewrite - /aleph_one; move => [pa pb pc]. move:(oclt pb) => pd. by move:(cardinal_indecomposable1 (cle_inf_inf h (proj1 pb)) pd) => []. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)