let E be set ; ==>.-relation ({} (E ^omega ),(E ^omega )) = {} (E ^omega ),(E ^omega )
A1:
==>.-relation ({} (E ^omega ),(E ^omega )) c= {} (E ^omega ),(E ^omega )
proof
let x be
set ;
TARSKI:def 3 ( not x in ==>.-relation ({} (E ^omega ),(E ^omega )) or x in {} (E ^omega ),(E ^omega ) )
assume A2:
x in ==>.-relation ({} (E ^omega ),(E ^omega ))
;
x in {} (E ^omega ),(E ^omega )
then consider a,
b being
set such that A3:
(
a in E ^omega &
b in E ^omega )
and A4:
x = [a,b]
by ZFMISC_1:def 2;
reconsider a =
a,
b =
b as
Element of
E ^omega by A3;
a ==>. b,
{} (E ^omega ),
(E ^omega )
by A2, A4, Def6;
hence
x in {} (E ^omega ),
(E ^omega )
by Th20;
verum
end;
{} (E ^omega ),(E ^omega ) = {}
by OPOSET_1:def 1;
then
{} (E ^omega ),(E ^omega ) c= ==>.-relation ({} (E ^omega ),(E ^omega ))
by XBOOLE_1:2;
hence
==>.-relation ({} (E ^omega ),(E ^omega )) = {} (E ^omega ),(E ^omega )
by A1, XBOOLE_0:def 10; verum