/2 width=5 by tri_TC_strap/ qed-.
lemma fqus_drop: ∀G1,G2,K1,K2,T1,T2. ⦃G1, K1, T1⦄ ⊐* ⦃G2, K2, T2⦄ →
- â\88\80L1,U1,e. â\87©[e] L1 â\89¡ K1 â\86\92 â\87§[0, e] T1 ≡ U1 →
+ â\88\80L1,U1,e. â¬\87[e] L1 â\89¡ K1 â\86\92 â¬\86[0, e] T1 ≡ U1 →
⦃G1, L1, U1⦄ ⊐* ⦃G2, K2, T2⦄.
#G1 #G2 #K1 #K2 #T1 #T2 #H @(fqus_ind … H) -G2 -K2 -T2
/3 width=5 by fqus_strap1, fquq_fqus, fquq_drop/