let GX be non empty TopSpace; ( ( for x, y being Point of GX ex h being Function of I[01],GX st
( h is continuous & x = h . 0 & y = h . 1 ) ) implies GX is connected )
assume A1:
for x, y being Point of GX ex h being Function of I[01],GX st
( h is continuous & x = h . 0 & y = h . 1 )
; GX is connected
for x, y being Point of GX ex GY being non empty TopSpace st
( GY is connected & ex f being Function of GY,GX st
( f is continuous & x in rng f & y in rng f ) )
proof
let x,
y be
Point of
GX;
ex GY being non empty TopSpace st
( GY is connected & ex f being Function of GY,GX st
( f is continuous & x in rng f & y in rng f ) )
now ex GY being non empty TopSpace st
( GY is connected & ex f being Function of GY,GX st
( f is continuous & x in rng f & y in rng f ) )consider h being
Function of
I[01],
GX such that A2:
h is
continuous
and A3:
x = h . 0
and A4:
y = h . 1
by A1;
A5:
0 in dom h
by Lm1, BORSUK_1:40, FUNCT_2:def 1;
A6:
1
in dom h
by Lm1, BORSUK_1:40, FUNCT_2:def 1;
A7:
x in rng h
by A3, A5, FUNCT_1:def 3;
y in rng h
by A4, A6, FUNCT_1:def 3;
hence
ex
GY being non
empty TopSpace st
(
GY is
connected & ex
f being
Function of
GY,
GX st
(
f is
continuous &
x in rng f &
y in rng f ) )
by A2, A7, TREAL_1:19;
verum end;
hence
ex
GY being non
empty TopSpace st
(
GY is
connected & ex
f being
Function of
GY,
GX st
(
f is
continuous &
x in rng f &
y in rng f ) )
;
verum
end;
hence
GX is connected
by TOPS_2:63; verum