(* Basic_1: uses: ty3_sn3 *)
(* Basic_2A1: uses: nta_fwd_csn *)
theorem nta_fwd_fsb (h) (a) (G) (L):
- â\88\80T,U. â¦\83G,Lâ¦\84 ⊢ T :[h,a] U →
- â\88§â\88§ â\89¥[h] ð\9d\90\92â¦\83G,L,Tâ¦\84 & â\89¥[h] ð\9d\90\92â¦\83G,L,Uâ¦\84.
+ â\88\80T,U. â\9dªG,Lâ\9d« ⊢ T :[h,a] U →
+ â\88§â\88§ â\89¥[h] ð\9d\90\92â\9dªG,L,Tâ\9d« & â\89¥[h] ð\9d\90\92â\9dªG,L,Uâ\9d«.
#h #a #G #L #T #U #H
elim (cnv_inv_cast … H) #X #HU #HT #_ #_ -X
/3 width=2 by cnv_fwd_fsb, conj/