X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fmatita%2Flibrary%2Fnat%2Frelevant_equations.ma;h=1c0f25f5770a34a2be644a093997a0fabc65a018;hb=8b55faddb06e3c4b0a13839210bb49170939b33e;hp=fee1fd4071a600027e5301d68979d2f15bf2bbff;hpb=5c6b8eec9db4119a87eb4fd4055f1ac31a713d90;p=helm.git

diff --git a/helm/matita/library/nat/relevant_equations.ma b/helm/matita/library/nat/relevant_equations.ma
index fee1fd407..1c0f25f57 100644
--- a/helm/matita/library/nat/relevant_equations.ma
+++ b/helm/matita/library/nat/relevant_equations.ma
@@ -15,6 +15,7 @@
 set "baseuri" "cic:/matita/nat/relevant_equations.ma".
 
 include "nat/times.ma".
+include "nat/minus.ma".
 
 theorem times_plus_l: \forall n,m,p:nat. (n+m)*p = n*p + m*p.
 intros.
@@ -27,6 +28,17 @@ apply sym_times.
 apply sym_times.
 qed.
 
+theorem times_minus_l: \forall n,m,p:nat. (n-m)*p = n*p - m*p.
+intros.
+apply trans_eq ? ? (p*(n-m)).
+apply sym_times.
+apply trans_eq ? ? (p*n-p*m).
+apply distr_times_minus.
+apply eq_f2.
+apply sym_times.
+apply sym_times.
+qed.
+
 theorem times_plus_plus: \forall n,m,p,q:nat. (n + m)*(p + q) =
 n*p + n*q + m*p + m*q.
 intros.