X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Flibrary%2FZ%2Ftimes.ma;h=58de9c82737871b27a4a67541268337975649132;hb=dd3157d36216486d914a97cfff7a9cd34f009ffe;hp=e5e1cdb452fa38ce33a8ba73f95b6ca4a5d5f27d;hpb=7f2444c2670cadafddd8785b687ef312158376b0;p=helm.git

diff --git a/matita/library/Z/times.ma b/matita/library/Z/times.ma
index e5e1cdb45..58de9c827 100644
--- a/matita/library/Z/times.ma
+++ b/matita/library/Z/times.ma
@@ -49,6 +49,7 @@ simplify.reflexivity.
 simplify.reflexivity.
 simplify.reflexivity.
 qed.
+
 theorem symmetric_Ztimes : symmetric Z Ztimes.
 change with (\forall x,y:Z. x*y = y*x).
 intros.elim x.rewrite > Ztimes_z_OZ.reflexivity.
@@ -68,7 +69,7 @@ variant sym_Ztimes : \forall x,y:Z. x*y = y*x
 \def symmetric_Ztimes.
 
 theorem associative_Ztimes: associative Z Ztimes.
-change with (\forall x,y,z:Z. (x*y)*z = x*(y*z)).
+unfold associative.
 intros.elim x.
   simplify.reflexivity. 
   elim y.