let W be Relation; for X being set st dom W c= X holds
*graph ((W,X) *graph) = W
let X be set ; ( dom W c= X implies *graph ((W,X) *graph) = W )
assume A1:
dom W c= X
; *graph ((W,X) *graph) = W
A2:
dom ((W,X) *graph) = X
by Def5;
now for x, y being object holds
( ( [x,y] in *graph ((W,X) *graph) implies [x,y] in W ) & ( [x,y] in W implies [x,y] in *graph ((W,X) *graph) ) )let x,
y be
object ;
( ( [x,y] in *graph ((W,X) *graph) implies [x,y] in W ) & ( [x,y] in W implies [x,y] in *graph ((W,X) *graph) ) )assume A3:
[x,y] in W
;
[x,y] in *graph ((W,X) *graph)then A4:
x in dom W
by XTUPLE_0:def 12;
x in {x}
by TARSKI:def 1;
then
y in Im (
W,
x)
by A3, RELAT_1:def 13;
then
y in ((W,X) *graph) . x
by A1, A4, Def5;
hence
[x,y] in *graph ((W,X) *graph)
by A1, A2, A4, Th38;
verum end;
hence
*graph ((W,X) *graph) = W
; verum