X-Git-Url: http://matita.cs.unibo.it/gitweb/?p=helm.git;a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Flib%2Fsubset_ext_equivalence.ma;h=07df6b3e9793b56732cb5a261ed7aa3db3ee5c4e;hp=28e4facc8fada42dea5249abc964c86f9f87a6e3;hb=8f1a123e61ff079b1f9ad63cc915470ec7e6abf3;hpb=df1bcd1387439133c0c33f597a5f8b2331c07772

diff --git a/matita/matita/contribs/lambdadelta/ground/lib/subset_ext_equivalence.ma b/matita/matita/contribs/lambdadelta/ground/lib/subset_ext_equivalence.ma
index 28e4facc8..07df6b3e9 100644
--- a/matita/matita/contribs/lambdadelta/ground/lib/subset_ext_equivalence.ma
+++ b/matita/matita/contribs/lambdadelta/ground/lib/subset_ext_equivalence.ma
@@ -30,6 +30,13 @@ lemma subset_equivalence_ext_f1_bi (A1) (A0) (f) (u1) (v1):
 /3 width=3 by subset_inclusion_ext_f1_bi, conj/
 qed.
 
+lemma subset_equivalence_ext_f1_1_bi (A11) (A21) (A0) (f1) (f2) (u11) (u21) (v11) (v21):
+      u11 ⇔ v11 → u21 ⇔ v21 →
+      subset_ext_f1_1 A11 A21 A0 f1 f2 u11 u21 ⇔ subset_ext_f1_1 A11 A21 A0 f1 f2 v11 v21.
+#A11 #A21 #A0 #f1 #f2 #u11 #u21 #v11 #v21 * #Huv11 #Hvu11 * #Huv21 #Hvu21
+/3 width=5 by subset_inclusion_ext_f1_1_bi, conj/
+qed.
+
 lemma subset_inclusion_ext_f1_compose (A0) (A1) (A2) (f1) (f2) (u):
       subset_ext_f1 A1 A2 f2 (subset_ext_f1 A0 A1 f1 u) ⇔ subset_ext_f1 A0 A2 (f2∘f1) u.
 /3 width=1 by subset_inclusion_ext_f1_compose_dx, subset_inclusion_ext_f1_compose_sn, conj/