DEFINITION subst1_confluence_eq() TYPE = ∀t0:T.∀t1:T.∀u:T.∀i:nat.(subst1 i u t0 t1)→∀t2:T.(subst1 i u t0 t2)→(ex2 T λt:T.subst1 i u t1 t λt:T.subst1 i u t2 t) BODY =Show proof