X-Git-Url: http://matita.cs.unibo.it/gitweb/?p=helm.git;a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Flib%2Fbool_and.ma;h=680ead78718faf9754e0c300989c8ddcb6088a1d;hp=b7a8bf96422c190db6ea808b4ba9342632ba0f67;hb=d06053844638d88936d711b66fddbcca2a9add1c;hpb=9e31ac1f3f868349154b0ce2e550e2476aaf6a30

diff --git a/matita/matita/contribs/lambdadelta/ground/lib/bool_and.ma b/matita/matita/contribs/lambdadelta/ground/lib/bool_and.ma
index b7a8bf964..680ead787 100644
--- a/matita/matita/contribs/lambdadelta/ground/lib/bool_and.ma
+++ b/matita/matita/contribs/lambdadelta/ground/lib/bool_and.ma
@@ -23,16 +23,27 @@ lemma commutative_andb:
 * * // qed.
 
 lemma andb_false_dx (b):
-      (b ∧ Ⓕ) = Ⓕ.
+      Ⓕ = (b ∧ Ⓕ).
 * // qed.
 
 lemma andb_false_sn (b):
-      (Ⓕ ∧ b) = Ⓕ.
+      Ⓕ = (Ⓕ ∧ b).
+// qed.
+
+lemma andb_true_dx (b):
+      b = (b ∧ Ⓣ).
+* // qed.
+
+lemma andb_true_sn (b):
+      b = (Ⓣ ∧ b).
 // qed.
 
 (* Advanced inversions ******************************************************)
 
-lemma andb_inv_true_dx (b1) (b2):
-      (b1 ∧ b2) = Ⓣ → ∧∧ b1 = Ⓣ & b2 = Ⓣ.
-* normalize /2 width=1 by conj/ #b2 #H destruct
+lemma andb_inv_true_sn (b1) (b2):
+      Ⓣ = (b1 ∧ b2) → ∧∧ Ⓣ = b1 & Ⓣ = b2.
+* normalize
+[ /2 width=1 by conj/
+| #b2 #H destruct
+]
 qed-.