1.1 --- a/src/HOL/Library/Product_Vector.thy	Thu Jan 31 12:09:07 2013 +0100
     1.2 +++ b/src/HOL/Library/Product_Vector.thy	Thu Jan 31 17:42:12 2013 +0100
     1.3 @@ -408,8 +408,6 @@
     1.4  
     1.5  instance proof
     1.6    fix r :: real and x y :: "'a \<times> 'b"
     1.7 -  show "0 \<le> norm x"
     1.8 -    unfolding norm_prod_def by simp
     1.9    show "norm x = 0 \<longleftrightarrow> x = 0"
    1.10      unfolding norm_prod_def
    1.11      by (simp add: prod_eq_iff)