lemma rex_lifts_bi (R):
d_liftable2_sn … lifts R →
∀L1,L2. |L1| = |L2| → ∀K1,K2,T. K1 ⪤[R,T] K2 →
- â\88\80b,f. â¬\87*[b,f] L1 â\89\98 K1 â\86\92 â¬\87*[b,f] L2 ≘ K2 →
- â\88\80U. â¬\86*[f] T ≘ U → L1 ⪤[R,U] L2.
+ â\88\80b,f. â\87©*[b,f] L1 â\89\98 K1 â\86\92 â\87©*[b,f] L2 ≘ K2 →
+ â\88\80U. â\87§*[f] T ≘ U → L1 ⪤[R,U] L2.
#R #HR #L1 #L2 #HL12 #K1 #K2 #T * #f1 #Hf1 #HK12 #b #f #HLK1 #HLK2 #U #HTU
elim (frees_total L1 U) #f2 #Hf2
lapply (frees_fwd_coafter … Hf2 … HLK1 … HTU … Hf1) -HTU #Hf