lemma rdeq_inv_lifts_sn: ∀h,o. f_dropable_sn (cdeq h o).
/2 width=5 by rex_dropable_sn/ qed-.
-(* Note: missing in basic_2A1 *)
lemma rdeq_inv_lifts_dx: ∀h,o. f_dropable_dx (cdeq h o).
/2 width=5 by rex_dropable_dx/ qed-.
-(* Basic_2A1: uses: lleq_inv_lift_le lleq_inv_lift_be lleq_inv_lift_ge *)
lemma rdeq_inv_lifts_bi: ∀h,o,L1,L2,U. L1 ≛[h, o, U] L2 → ∀b,f. 𝐔⦃f⦄ →
∀K1,K2. ⬇*[b, f] L1 ≘ K1 → ⬇*[b, f] L2 ≘ K2 →
∀T. ⬆*[f] T ≘ U → K1 ≛[h, o, T] K2.