let X be non empty TopSpace; for a, b being Point of X st a,b are_connected holds
( not EqRel X,a,b is empty & EqRel X,a,b is total & EqRel X,a,b is symmetric & EqRel X,a,b is transitive )
let a, b be Point of X; ( a,b are_connected implies ( not EqRel X,a,b is empty & EqRel X,a,b is total & EqRel X,a,b is symmetric & EqRel X,a,b is transitive ) )
set E = EqRel X,a,b;
set W = Paths a,b;
assume A1:
a,b are_connected
; ( not EqRel X,a,b is empty & EqRel X,a,b is total & EqRel X,a,b is symmetric & EqRel X,a,b is transitive )
then consider EqR being Equivalence_Relation of (Paths a,b) such that
A2:
for x, y being set holds
( [x,y] in EqR iff ( x in Paths a,b & y in Paths a,b & ex P, Q being Path of a,b st
( P = x & Q = y & P,Q are_homotopic ) ) )
by Lm2;
EqRel X,a,b = EqR
proof
let x,
y be
set ;
RELAT_1:def 2 ( ( not [x,y] in EqRel X,a,b or [x,y] in EqR ) & ( not [x,y] in EqR or [x,y] in EqRel X,a,b ) )
thus
(
[x,y] in EqRel X,
a,
b implies
[x,y] in EqR )
( not [x,y] in EqR or [x,y] in EqRel X,a,b )proof
assume A3:
[x,y] in EqRel X,
a,
b
;
[x,y] in EqR
then A4:
(
x in Paths a,
b &
y in Paths a,
b )
by ZFMISC_1:106;
then reconsider x =
x,
y =
y as
Path of
a,
b by Def1;
x,
y are_homotopic
by A1, A3, Def3;
hence
[x,y] in EqR
by A2, A4;
verum
end;
assume A5:
[x,y] in EqR
;
[x,y] in EqRel X,a,b
then
(
x in Paths a,
b &
y in Paths a,
b )
by ZFMISC_1:106;
then reconsider x =
x,
y =
y as
Path of
a,
b by Def1;
ex
P,
Q being
Path of
a,
b st
(
P = x &
Q = y &
P,
Q are_homotopic )
by A2, A5;
hence
[x,y] in EqRel X,
a,
b
by A1, Def3;
verum
end;
hence
( not EqRel X,a,b is empty & EqRel X,a,b is total & EqRel X,a,b is symmetric & EqRel X,a,b is transitive )
by EQREL_1:16, RELAT_1:63; verum