X-Git-Url: http://matita.cs.unibo.it/gitweb/?p=helm.git;a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground_2%2Fxoa%2Fxoa_props.ma;h=530c0e2b39541f81f971847c667b4f317a41a108;hp=408e1933dec9e3c55744a695c6c63f6a22e8238e;hb=8653dd54c57943e28e3ef60d2d0cbc1861a76a33;hpb=bf7be462a06e739b39af20f72362857e849a2aa0

diff --git a/matita/matita/contribs/lambdadelta/ground_2/xoa/xoa_props.ma b/matita/matita/contribs/lambdadelta/ground_2/xoa/xoa_props.ma
index 408e1933d..530c0e2b3 100644
--- a/matita/matita/contribs/lambdadelta/ground_2/xoa/xoa_props.ma
+++ b/matita/matita/contribs/lambdadelta/ground_2/xoa/xoa_props.ma
@@ -22,3 +22,9 @@ include "ground_2/xoa/xoa.ma".
 interpretation "logical false" 'false = False.
 
 interpretation "logical true" 'true = True.
+
+(* Logical properties missing in the basic library **************************) 
+
+lemma commutative_and: ∀A,B. A ∧ B → B ∧ A.
+#A #B * /2 width=1 by conj/
+qed-.