--- a/src/HOL/ex/Lagrange.ML Fri Nov 29 15:07:27 1996 +0100
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,18 +0,0 @@
-(* Title: HOL/ex/Lagrange.ML
- ID: $Id$
- Author: Tobias Nipkow
- Copyright 1996 TU Muenchen
-
-
-The following lemma schows that all composite natural numbers are sums of
-fours squares, provided all prime numbers are.
-*)
-
-goalw Lagrange.thy [Lagrange.sq_def] "!!x1::'a::cring. \
-\ (sq x1 + sq x2 + sq x3 + sq x4) * (sq y1 + sq y2 + sq y3 + sq y4) = \
-\ sq(x1*y1 - x2*y2 - x3*y3 - x4*y4) + \
-\ sq(x1*y2 + x2*y1 + x3*y4 - x4*y3) + \
-\ sq(x1*y3 - x2*y4 + x3*y1 + x4*y2) + \
-\ sq(x1*y4 + x2*y3 - x3*y2 + x4*y1)";
-by(cring_simp 1);
-qed "Lagrange_lemma";