let R be Ring; for a being Element of R holds Class (EqRel R,([#] R)),a = the carrier of R
let a be Element of R; Class (EqRel R,([#] R)),a = the carrier of R
set E = EqRel R,([#] R);
thus
Class (EqRel R,([#] R)),a c= the carrier of R
; XBOOLE_0:def 10 the carrier of R c= Class (EqRel R,([#] R)),a
let x be set ; TARSKI:def 3 ( not x in the carrier of R or x in Class (EqRel R,([#] R)),a )
assume
x in the carrier of R
; x in Class (EqRel R,([#] R)),a
then reconsider x = x as Element of R ;
x - a in [#] R
;
then
[x,a] in EqRel R,([#] R)
by Def5;
hence
x in Class (EqRel R,([#] R)),a
by EQREL_1:27; verum