let L be lower-bounded LATTICE; ( L has_a_representation_of_type<= 2 implies L is modular )
assume
L has_a_representation_of_type<= 2
; L is modular
then consider A being non trivial set , f being Homomorphism of L,(EqRelLATT A) such that
A1:
f is one-to-one
and
A2:
( Image f is finitely_typed & ex e being Equivalence_Relation of A st
( e in the carrier of (Image f) & e <> id A ) & type_of (Image f) <= 2 )
;
A3:
( rng (corestr f) = the carrier of (Image f) & ( for x, y being Element of L st x <= y holds
(corestr f) . x <= (corestr f) . y ) )
by FUNCT_2:def 3, WAYBEL_1:def 2;
( corestr f is one-to-one & ( for x, y being Element of L st (corestr f) . x <= (corestr f) . y holds
x <= y ) )
by A1, Th7, WAYBEL_1:30;
then
corestr f is isomorphic
by A3, WAYBEL_0:66;
then A4:
L, Image f are_isomorphic
by WAYBEL_1:def 8;
A5:
Image f is lower-bounded LATTICE
by Th6;
Image f is modular
by A2, Th8;
hence
L is modular
by A5, A4, Th5, WAYBEL_1:6; verum