proposition: Lemma regular_initial_limit2 x: limit_ordinal x -> \cf(\aleph x) <=o x.
proof: Proof. move=> lx; move: (regular_initial_limit0 lx) => pa. exact: (oleT pa (cofinality_pr3 (proj31 lx))). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)