--- a/src/HOL/Relation.thy Mon Aug 31 20:34:44 2009 +0200
+++ b/src/HOL/Relation.thy Mon Aug 31 20:34:48 2009 +0200
@@ -599,6 +599,9 @@
apply blast
done
+lemma in_inv_image[simp]: "((x,y) : inv_image r f) = ((f x, f y) : r)"
+ by (auto simp:inv_image_def)
+
subsection {* Finiteness *}