let P be non empty Subset of (TOP-REAL 2); for Q being Subset of ((TOP-REAL 2) | P)
for p1, p2, q being Point of (TOP-REAL 2) st P is_an_arc_of p1,p2 & q in P & q <> p1 & q <> p2 & Q = P \ {q} holds
( not Q is connected & ( for R being Function of I[01],(((TOP-REAL 2) | P) | Q) holds
( not R is continuous or not R . 0 = p1 or not R . 1 = p2 ) ) )
let Q be Subset of ((TOP-REAL 2) | P); for p1, p2, q being Point of (TOP-REAL 2) st P is_an_arc_of p1,p2 & q in P & q <> p1 & q <> p2 & Q = P \ {q} holds
( not Q is connected & ( for R being Function of I[01],(((TOP-REAL 2) | P) | Q) holds
( not R is continuous or not R . 0 = p1 or not R . 1 = p2 ) ) )
let p1, p2, q be Point of (TOP-REAL 2); ( P is_an_arc_of p1,p2 & q in P & q <> p1 & q <> p2 & Q = P \ {q} implies ( not Q is connected & ( for R being Function of I[01],(((TOP-REAL 2) | P) | Q) holds
( not R is continuous or not R . 0 = p1 or not R . 1 = p2 ) ) ) )
assume that
A1:
P is_an_arc_of p1,p2
and
A2:
q in P
and
A3:
q <> p1
and
A4:
q <> p2
and
A5:
Q = P \ {q}
; ( not Q is connected & ( for R being Function of I[01],(((TOP-REAL 2) | P) | Q) holds
( not R is continuous or not R . 0 = p1 or not R . 1 = p2 ) ) )
consider f being Function of I[01],((TOP-REAL 2) | P) such that
A6:
f is being_homeomorphism
and
A7:
f . 0 = p1
and
A8:
f . 1 = p2
by A1, TOPREAL1:def 1;
A9:
rng f = [#] ((TOP-REAL 2) | P)
by A6, TOPS_2:def 5;
A10:
[#] I[01] = [.0,1.]
by TOPMETR:18, TOPMETR:20;
A11:
[#] ((TOP-REAL 2) | P) = P
by PRE_TOPC:def 5;
then consider xs being object such that
A12:
xs in dom f
and
A13:
f . xs = q
by A2, A9, FUNCT_1:def 3;
A14:
dom f = [#] I[01]
by A6, TOPS_2:def 5;
reconsider s = xs as Real by A12;
{ q0 where q0 is Point of (TOP-REAL 2) : ex ss being Real st
( s < ss & ss <= 1 & q0 = f . ss ) } c= the carrier of ((TOP-REAL 2) | P)
then reconsider P29 = { q0 where q0 is Point of (TOP-REAL 2) : ex ss being Real st
( s < ss & ss <= 1 & q0 = f . ss ) } as Subset of ((TOP-REAL 2) | P) ;
A20:
0 <= s
by A12, A10, XXREAL_1:1;
then A21:
P29 is open
by A6, Th16;
A22:
P29 c= Q
proof
let x be
object ;
TARSKI:def 3 ( not x in P29 or x in Q )
assume
x in P29
;
x in Q
then consider q00 being
Point of
(TOP-REAL 2) such that A23:
q00 = x
and A24:
ex
ss being
Real st
(
s < ss &
ss <= 1 &
q00 = f . ss )
;
consider ss being
Real such that A25:
s < ss
and A26:
ss <= 1
and A27:
q00 = f . ss
by A24;
ss > 0
by A12, A10, A25, XXREAL_1:1;
then A28:
ss in dom f
by A14, A10, A26, XXREAL_1:1;
then A30:
not
q00 in {q}
by TARSKI:def 1;
q00 in P
by A9, A11, A27, A28, FUNCT_1:def 3;
hence
x in Q
by A5, A23, A30, XBOOLE_0:def 5;
verum
end;
{ q0 where q0 is Point of (TOP-REAL 2) : ex ss being Real st
( 0 <= ss & ss < s & q0 = f . ss ) } c= the carrier of ((TOP-REAL 2) | P)
then reconsider P19 = { q0 where q0 is Point of (TOP-REAL 2) : ex ss being Real st
( 0 <= ss & ss < s & q0 = f . ss ) } as Subset of ((TOP-REAL 2) | P) ;
A36:
s <= 1
by A12, A10, XXREAL_1:1;
then A37:
P19 is open
by A6, Th15;
A38:
Q c= P19 \/ P29
A45:
now not P19 meets P29assume
P19 meets P29
;
contradictionthen consider p0 being
object such that A46:
p0 in P19
and A47:
p0 in P29
by XBOOLE_0:3;
consider q00 being
Point of
(TOP-REAL 2) such that A48:
q00 = p0
and A49:
ex
ss being
Real st
(
0 <= ss &
ss < s &
q00 = f . ss )
by A46;
consider ss1 being
Real such that A50:
0 <= ss1
and A51:
ss1 < s
and A52:
q00 = f . ss1
by A49;
ss1 < 1
by A36, A51, XXREAL_0:2;
then A53:
ss1 in dom f
by A14, A10, A50, XXREAL_1:1;
consider q01 being
Point of
(TOP-REAL 2) such that A54:
q01 = p0
and A55:
ex
ss being
Real st
(
s < ss &
ss <= 1 &
q01 = f . ss )
by A47;
consider ss2 being
Real such that A56:
s < ss2
and A57:
ss2 <= 1
and A58:
q01 = f . ss2
by A55;
ss2 > 0
by A12, A10, A56, XXREAL_1:1;
then A59:
ss2 in dom f
by A14, A10, A57, XXREAL_1:1;
f is
one-to-one
by A6, TOPS_2:def 5;
hence
contradiction
by A48, A51, A52, A54, A56, A58, A53, A59, FUNCT_1:def 4;
verum end;
1 > s
by A4, A8, A13, A36, XXREAL_0:1;
then A60:
p2 in { q0 where q0 is Point of (TOP-REAL 2) : ex ss being Real st
( s < ss & ss <= 1 & q0 = f . ss ) }
by A8;
then reconsider Q9 = Q as non empty Subset of ((TOP-REAL 2) | P) by A22;
reconsider T = ((TOP-REAL 2) | P) | Q9 as non empty TopSpace ;
A61:
the carrier of T = [#] T
;
then reconsider P299 = P29 as Subset of T by A22, PRE_TOPC:def 5;
P29 /\ Q <> {}
by A60, A22, XBOOLE_1:28;
then A62:
P29 meets Q
by XBOOLE_0:def 7;
A63:
P19 c= Q
proof
let x be
object ;
TARSKI:def 3 ( not x in P19 or x in Q )
assume
x in P19
;
x in Q
then consider q00 being
Point of
(TOP-REAL 2) such that A64:
q00 = x
and A65:
ex
ss being
Real st
(
0 <= ss &
ss < s &
q00 = f . ss )
;
consider ss being
Real such that A66:
0 <= ss
and A67:
ss < s
and A68:
q00 = f . ss
by A65;
ss < 1
by A36, A67, XXREAL_0:2;
then A69:
ss in dom f
by A14, A10, A66, XXREAL_1:1;
then A71:
not
q00 in {q}
by TARSKI:def 1;
q00 in P
by A9, A11, A68, A69, FUNCT_1:def 3;
hence
x in Q
by A5, A64, A71, XBOOLE_0:def 5;
verum
end;
then reconsider P199 = P19 as Subset of T by A61, PRE_TOPC:def 5;
P199 = P19 /\ the carrier of T
by XBOOLE_1:28;
then A72:
P199 is open
by A37, A61, TOPS_2:24;
s <> 0
by A3, A7, A13;
then A73:
p1 in { q0 where q0 is Point of (TOP-REAL 2) : ex ss being Real st
( 0 <= ss & ss < s & q0 = f . ss ) }
by A7, A20;
then
P19 /\ Q <> {}
by A63, XBOOLE_1:28;
then
P19 meets Q
by XBOOLE_0:def 7;
hence
not Q is connected
by A37, A21, A38, A62, A45, TOPREAL5:1; for R being Function of I[01],(((TOP-REAL 2) | P) | Q) holds
( not R is continuous or not R . 0 = p1 or not R . 1 = p2 )
the carrier of T = Q
by A61, PRE_TOPC:def 5;
then A74:
P199 \/ P299 = the carrier of (((TOP-REAL 2) | P) | Q)
by A38, XBOOLE_0:def 10;
P299 = P29 /\ the carrier of T
by XBOOLE_1:28;
then A75:
P299 is open
by A21, A61, TOPS_2:24;
P199 /\ P299 = {}
by A45, XBOOLE_0:def 7;
hence
for R being Function of I[01],(((TOP-REAL 2) | P) | Q) holds
( not R is continuous or not R . 0 = p1 or not R . 1 = p2 )
by A73, A60, A72, A75, A74, Th17; verum