let L be complete LATTICE; for R being non empty Subset of [:L,L:] st R is CLCongruence holds
for x being Element of L holds [(inf (Class (EqRel R),x)),x] in R
let R be non empty Subset of [:L,L:]; ( R is CLCongruence implies for x being Element of L holds [(inf (Class (EqRel R),x)),x] in R )
assume A1:
R is CLCongruence
; for x being Element of L holds [(inf (Class (EqRel R),x)),x] in R
let x be Element of L; [(inf (Class (EqRel R),x)),x] in R
set CRx = Class (EqRel R),x;
reconsider SR = [:(Class (EqRel R),x),{x}:] as Subset of [:L,L:] ;
R is Equivalence_Relation of the carrier of L
by A1, Def2;
then A2:
R = EqRel R
by Def1;
SR c= the carrier of (subrelstr R)
then reconsider SR9 = SR as Subset of (subrelstr R) ;
A6:
ex_inf_of SR,[:L,L:]
by YELLOW_0:17;
subrelstr R is CLSubFrame of [:L,L:]
by A1, Def2;
then A7:
"/\" SR9,[:L,L:] in the carrier of (subrelstr R)
by A6, YELLOW_0:def 18;
A8:
x in Class (EqRel R),x
by EQREL_1:28;
inf SR =
[(inf (proj1 SR)),(inf (proj2 SR))]
by Th7, YELLOW_0:17
.=
[(inf (Class (EqRel R),x)),(inf (proj2 SR))]
by FUNCT_5:11
.=
[(inf (Class (EqRel R),x)),(inf {x})]
by A8, FUNCT_5:11
.=
[(inf (Class (EqRel R),x)),x]
by YELLOW_0:39
;
hence
[(inf (Class (EqRel R),x)),x] in R
by A7, YELLOW_0:def 15; verum