let S, T be non empty TopSpace; :: thesis: for T1, T2 being SubSpace of T
for p1, p2 being Point of T
for f being Function of T1,S
for g being Function of T2,S st ([#] T1) \/ ([#] T2) = [#] T & ([#] T1) /\ ([#] T2) = {p1,p2} & T1 is compact & T2 is compact & T is Hausdorff & f is continuous & g is continuous & f . p1 = g . p1 & f . p2 = g . p2 holds
f +* g is continuous Function of T,S
let T1, T2 be SubSpace of T; :: thesis: for p1, p2 being Point of T
for f being Function of T1,S
for g being Function of T2,S st ([#] T1) \/ ([#] T2) = [#] T & ([#] T1) /\ ([#] T2) = {p1,p2} & T1 is compact & T2 is compact & T is Hausdorff & f is continuous & g is continuous & f . p1 = g . p1 & f . p2 = g . p2 holds
f +* g is continuous Function of T,S
let p1, p2 be Point of T; :: thesis: for f being Function of T1,S
for g being Function of T2,S st ([#] T1) \/ ([#] T2) = [#] T & ([#] T1) /\ ([#] T2) = {p1,p2} & T1 is compact & T2 is compact & T is Hausdorff & f is continuous & g is continuous & f . p1 = g . p1 & f . p2 = g . p2 holds
f +* g is continuous Function of T,S
let f be Function of T1,S; :: thesis: for g being Function of T2,S st ([#] T1) \/ ([#] T2) = [#] T & ([#] T1) /\ ([#] T2) = {p1,p2} & T1 is compact & T2 is compact & T is Hausdorff & f is continuous & g is continuous & f . p1 = g . p1 & f . p2 = g . p2 holds
f +* g is continuous Function of T,S
let g be Function of T2,S; :: thesis: ( ([#] T1) \/ ([#] T2) = [#] T & ([#] T1) /\ ([#] T2) = {p1,p2} & T1 is compact & T2 is compact & T is Hausdorff & f is continuous & g is continuous & f . p1 = g . p1 & f . p2 = g . p2 implies f +* g is continuous Function of T,S )
assume that
A1:
( ([#] T1) \/ ([#] T2) = [#] T & ([#] T1) /\ ([#] T2) = {p1,p2} )
and
A2:
T1 is compact
and
A3:
T2 is compact
and
A4:
T is Hausdorff
and
A5:
f is continuous
and
A6:
g is continuous
and
A7:
( f . p1 = g . p1 & f . p2 = g . p2 )
; :: thesis: f +* g is continuous Function of T,S
set h = f +* g;
A8:
dom f = [#] T1
by FUNCT_2:def 1;
A9:
dom g = [#] T2
by FUNCT_2:def 1;
then A10:
dom (f +* g) = the carrier of T
by A1, A8, FUNCT_4:def 1;
( (rng f) \/ (rng g) c= the carrier of S & rng (f +* g) c= (rng f) \/ (rng g) )
by FUNCT_4:18;
then
rng (f +* g) c= the carrier of S
by XBOOLE_1:1;
then reconsider h = f +* g as Function of T,S by A10, FUNCT_2:def 1, RELSET_1:11;
for P being Subset of S st P is closed holds
h " P is closed
proof
let P be
Subset of
S;
:: thesis: ( P is closed implies h " P is closed )
assume A11:
P is
closed
;
:: thesis: h " P is closed
A12:
(
h " P c= dom h &
dom h = (dom f) \/ (dom g) )
by FUNCT_4:def 1, RELAT_1:167;
then A13:
h " P =
(h " P) /\ (([#] T1) \/ ([#] T2))
by A8, A9, XBOOLE_1:28
.=
((h " P) /\ ([#] T1)) \/ ((h " P) /\ ([#] T2))
by XBOOLE_1:23
;
A14:
for
x being
set st
x in [#] T1 holds
h . x = f . x
then A18:
(h " P) /\ ([#] T1) = f " P
by TARSKI:2;
then A19:
h " P = (f " P) \/ (g " P)
by A13, A18, TARSKI:2;
(
f " P c= [#] T1 &
[#] T1 c= [#] T )
by A1, XBOOLE_1:7;
then reconsider P1 =
f " P as
Subset of
T by XBOOLE_1:1;
(
g " P c= [#] T2 &
[#] T2 c= [#] T )
by A1, XBOOLE_1:7;
then reconsider P2 =
g " P as
Subset of
T by XBOOLE_1:1;
(
f " P is
closed &
g " P is
closed )
by A5, A6, A11, PRE_TOPC:def 12;
then
(
f " P is
compact &
g " P is
compact )
by A2, A3, Th17;
then
(
P1 is
compact &
P2 is
compact )
by Th42;
hence
h " P is
closed
by A4, A19, Th16, Th19;
:: thesis: verum
end;
hence
f +* g is continuous Function of T,S
by PRE_TOPC:def 12; :: thesis: verum