let A, P be Subset of (TOP-REAL 2); ( P is compact & |[(- 1),0]|,|[1,0]| realize-max-dist-in P & A is_inside_component_of P implies A c= closed_inside_of_rectangle ((- 1),1,(- 3),3) )
assume that
A1:
P is compact
and
A2:
|[(- 1),0]|,|[1,0]| realize-max-dist-in P
and
A3:
A is_inside_component_of P
; A c= closed_inside_of_rectangle ((- 1),1,(- 3),3)
let x be object ; TARSKI:def 3 ( not x in A or x in closed_inside_of_rectangle ((- 1),1,(- 3),3) )
assume that
A4:
x in A
and
A5:
not x in closed_inside_of_rectangle ((- 1),1,(- 3),3)
; contradiction
P c= closed_inside_of_rectangle ((- 1),1,(- 3),3)
by A2, Th71;
then A6:
(closed_inside_of_rectangle ((- 1),1,(- 3),3)) ` c= P `
by SUBSET_1:12;
reconsider x = x as Point of (TOP-REAL 2) by A4;
A7:
( not - 1 <= x `1 or not x `1 <= 1 or not - 3 <= x `2 or not x `2 <= 3 )
by A5;
per cases
( 0 <= x `1 or x `1 < 0 )
;
suppose A8:
0 <= x `1
;
contradictionset E =
east_halfline x;
east_halfline x c= (closed_inside_of_rectangle ((- 1),1,(- 3),3)) `
proof
let e be
object ;
TARSKI:def 3 ( not e in east_halfline x or e in (closed_inside_of_rectangle ((- 1),1,(- 3),3)) ` )
assume A9:
e in east_halfline x
;
e in (closed_inside_of_rectangle ((- 1),1,(- 3),3)) `
then reconsider e =
e as
Point of
(TOP-REAL 2) ;
A10:
e `1 >= x `1
by A9, TOPREAL1:def 11;
hence
e in (closed_inside_of_rectangle ((- 1),1,(- 3),3)) `
by SUBSET_1:29;
verum
end; then
east_halfline x c= P `
by A6;
then
east_halfline x misses P
by SUBSET_1:23;
then A11:
east_halfline x c= UBD P
by A1, JORDAN2C:127;
x in east_halfline x
by TOPREAL1:38;
then
A meets UBD P
by A4, A11, XBOOLE_0:3;
hence
contradiction
by A3, Th14;
verum end; suppose A12:
x `1 < 0
;
contradictionset E =
west_halfline x;
west_halfline x c= (closed_inside_of_rectangle ((- 1),1,(- 3),3)) `
proof
let e be
object ;
TARSKI:def 3 ( not e in west_halfline x or e in (closed_inside_of_rectangle ((- 1),1,(- 3),3)) ` )
assume A13:
e in west_halfline x
;
e in (closed_inside_of_rectangle ((- 1),1,(- 3),3)) `
then reconsider e =
e as
Point of
(TOP-REAL 2) ;
A14:
e `1 <= x `1
by A13, TOPREAL1:def 13;
hence
e in (closed_inside_of_rectangle ((- 1),1,(- 3),3)) `
by SUBSET_1:29;
verum
end; then
west_halfline x c= P `
by A6;
then
west_halfline x misses P
by SUBSET_1:23;
then A15:
west_halfline x c= UBD P
by A1, JORDAN2C:126;
x in west_halfline x
by TOPREAL1:38;
then
A meets UBD P
by A4, A15, XBOOLE_0:3;
hence
contradiction
by A3, Th14;
verum end; end;