-lemma cix_inv_ib2: ∀h,g,a,I,G,L,V,T. ib2 a I → ⦃G, L⦄ ⊢ 𝐈[h, g]⦃ⓑ{a,I}V.T⦄ →
- ⦃G, L⦄ ⊢ 𝐈[h, g]⦃V⦄ ∧ ⦃G, L.ⓑ{I}V⦄ ⊢ 𝐈[h, g]⦃T⦄.
-/4 width=1/ qed-.
+lemma cix_inv_ib2: ∀h,g,a,I,G,L,V,T. ib2 a I → ⦃G, L⦄ ⊢ ➡[h, g] 𝐈⦃ⓑ{a,I}V.T⦄ →
+ ⦃G, L⦄ ⊢ ➡[h, g] 𝐈⦃V⦄ ∧ ⦃G, L.ⓑ{I}V⦄ ⊢ ➡[h, g] 𝐈⦃T⦄.
+/4 width=1 by crx_ib2_sn, crx_ib2_dx, conj/ qed-.