changeset 44345 | 881c324470a2 |
parent 43531 | cc46a678faaf |
child 44766 | d4d33a4d7548 |
--- a/src/HOL/Nat_Numeral.thy Sat Aug 20 07:09:44 2011 -0700 +++ b/src/HOL/Nat_Numeral.thy Sat Aug 20 09:59:28 2011 -0700 @@ -129,6 +129,14 @@ end +context idom +begin + +lemma power2_eq_iff: "x\<twosuperior> = y\<twosuperior> \<longleftrightarrow> x = y \<or> x = - y" + unfolding power2_eq_square by (rule square_eq_iff) + +end + context linordered_ring begin