New proofs.

diff --git a/helm/software/matita/nlibrary/basics/list.ma b/helm/software/matita/nlibrary/basics/list.ma
index b5664d1341e13562510002b40d4720f22165d3ac..92eddc705b642fb8f984d55c2aea81dc62d68cb1 100644 (file)
--- a/helm/software/matita/nlibrary/basics/list.ma
+++ b/helm/software/matita/nlibrary/basics/list.ma
@@ -79,7 +79,9 @@ ntheorem cons_append_commute:
 //; nqed.
 
 ntheorem append_cons:∀A.∀a:A.∀l,l1.l@(a::l1)=(l@[a])@l1.
-/2/; nqed.
+#A; #a; #l; #l1; napply symmetric_eq.
+napply associative_append.
+(* /2/; *) nqed.
 
 ntheorem nil_append_elim: ∀A.∀l1,l2: list A.∀P: list A → list A → Prop. 
   l1@l2 = [] → P (nil A) (nil A) → P l1 l2.