Few theorems added.`

[helm.git] / matita / library / nat / plus.ma

diff --git a/matita/library/nat/plus.ma b/matita/library/nat/plus.ma
index d595dad19113cb6626ec4e58cc1e8a2d389be2b1..e8b5f6d29e258cee77866c26a470f6cc4119bef5 100644 (file)
--- a/matita/library/nat/plus.ma
+++ b/matita/library/nat/plus.ma
@@ -36,6 +36,11 @@ simplify.reflexivity.
 simplify.apply eq_f.assumption.
 qed.
 
+theorem plus_n_SO : \forall n:nat. S n = n+(S O).
+intro.rewrite > plus_n_O.
+apply plus_n_Sm.
+qed.
+
 theorem sym_plus: \forall n,m:nat. n+m = m+n.
 intros.elim n.
 simplify.apply plus_n_O.