src/HOL/Hilbert_Choice.thy
changeset 26105 ae06618225ec
parent 26072 f65a7fa2da6c
child 26347 105f55201077
     1.1 --- a/src/HOL/Hilbert_Choice.thy	Wed Feb 20 23:24:38 2008 +0100
     1.2 +++ b/src/HOL/Hilbert_Choice.thy	Thu Feb 21 17:33:58 2008 +0100
     1.3 @@ -268,6 +268,11 @@
     1.4    apply (simp add: Inv_mem)
     1.5    done
     1.6  
     1.7 +lemma bij_betw_Inv: "bij_betw f A B \<Longrightarrow> bij_betw (Inv A f) B A"
     1.8 +  apply (auto simp add: bij_betw_def inj_on_Inv Inv_mem)
     1.9 +  apply (simp add: image_compose [symmetric] o_def)
    1.10 +  apply (simp add: image_def Inv_f_f)
    1.11 +  done
    1.12  
    1.13  subsection {*Other Consequences of Hilbert's Epsilon*}
    1.14