let L be non empty reflexive transitive RelStr ; ( ( for x being Element of L
for N being net of L st N is eventually-directed holds
x "/\" (sup N) = sup ({x} "/\" (rng (netmap N,L))) ) implies L is satisfying_MC )
assume A1:
for x being Element of L
for N being net of L st N is eventually-directed holds
x "/\" (sup N) = sup ({x} "/\" (rng (netmap N,L)))
; L is satisfying_MC
let x be Element of L; WAYBEL_2:def 6 for b1 being Element of K10(the carrier of L) holds x "/\" ("\/" b1,L) = "\/" ({x} "/\" b1),L
let D be non empty directed Subset of L; x "/\" ("\/" D,L) = "\/" ({x} "/\" D),L
reconsider n = id D as Function of D,the carrier of L by FUNCT_2:9;
set N = NetStr(# D,(the InternalRel of L |_2 D),n #);
A2:
( NetStr(# D,(the InternalRel of L |_2 D),n #) is eventually-directed & Sup = sup NetStr(# D,(the InternalRel of L |_2 D),n #) )
by WAYBEL_2:20;
D c= D
;
then A3: D =
n .: D
by FUNCT_1:162
.=
rng (netmap NetStr(# D,(the InternalRel of L |_2 D),n #),L)
by FUNCT_2:45
;
hence x "/\" (sup D) =
x "/\" (Sup )
by YELLOW_2:def 5
.=
sup ({x} "/\" D)
by A1, A3, A2
;
verum