let G1 be _Graph; for G2 being LGraphComplement of G1 st the_Edges_of G1 = G1 .loops() holds
G2 is complete
let G2 be LGraphComplement of G1; ( the_Edges_of G1 = G1 .loops() implies G2 is complete )
assume A1:
the_Edges_of G1 = G1 .loops()
; G2 is complete
now for v, w being Vertex of G2 st v <> w holds
v,w are_adjacent let v,
w be
Vertex of
G2;
( v <> w implies v,w are_adjacent )A2:
(
v is
Vertex of
G1 &
w is
Vertex of
G1 )
by Def7;
assume A3:
v <> w
;
v,w are_adjacent
for
e1 being
object holds not
e1 Joins v,
w,
G1
then consider e2 being
object such that A5:
e2 Joins v,
w,
G2
by A2, Def7;
thus
v,
w are_adjacent
by A5, CHORD:def 3;
verum end;
hence
G2 is complete
by CHORD:def 6; verum