:: More on External Approximation of a Continuum
:: by Andrzej Trybulec
::
:: Received October 7, 2001
:: Copyright (c) 2001 Association of Mizar Users

begin

registration

let D be non empty with_non-empty_element set ;
cluster non empty Relation-like non-empty NAT -defined D * -valued Function-like finite FinSequence-like FinSubsequence-like Function-yielding FinSequence-yielding finite-support FinSequence of D * ;
existence
ex b₁ being FinSequence of D * st
( not b₁ is empty & b₁ is non-empty )

proof end;

end;

registration

let F be non-empty Function-yielding Function;
cluster rngs F -> non-empty ;
coherence
rngs F is non-empty

proof end;

end;

theorem :: JORDAN1H:1

canceled;

theorem :: JORDAN1H:2

canceled;

theorem :: JORDAN1H:3

canceled;

theorem :: JORDAN1H:4

canceled;

theorem :: JORDAN1H:5

canceled;

theorem Th6: :: JORDAN1H:6

for p, q being Point of (TOP-REAL 2) st p <> q holds
p in Cl ((LSeg (p,q)) \ {p,q})

proof end;

theorem Th7: :: JORDAN1H:7

for p, q being Point of (TOP-REAL 2) st p <> q holds
Cl ((LSeg (p,q)) \ {p,q}) = LSeg (p,q)

proof end;

theorem :: JORDAN1H:8

for S being Subset of (TOP-REAL 2)
for p, q being Point of (TOP-REAL 2) st p <> q & (LSeg (p,q)) \ {p,q} c= S holds
LSeg (p,q) c= Cl S

proof end;

begin

definition

func RealOrd -> Relation of REAL equals :: JORDAN1H:def 1
{ [r,s] where r, s is Real : r <= s } ;
coherence
{ [r,s] where r, s is Real : r <= s } is Relation of REAL

proof end;

end;

:: deftheorem defines RealOrd JORDAN1H:def 1 :
RealOrd = { [r,s] where r, s is Real : r <= s } ;

theorem Th9: :: JORDAN1H:9

for r, s being Real st [r,s] in RealOrd holds
r <= s

proof end;

Lm1: RealOrd is_reflexive_in REAL

proof end;

Lm2: RealOrd is_antisymmetric_in REAL

proof end;

Lm3: RealOrd is_transitive_in REAL

proof end;

Lm4: RealOrd is_connected_in REAL

proof end;

theorem Th10: :: JORDAN1H:10

field RealOrd = REAL

proof end;

registration

cluster RealOrd -> total reflexive antisymmetric transitive being_linear-order ;
coherence
( RealOrd is total & RealOrd is reflexive & RealOrd is antisymmetric & RealOrd is transitive & RealOrd is being_linear-order )

proof end;

end;

theorem Th11: :: JORDAN1H:11

RealOrd linearly_orders REAL

proof end;

theorem Th12: :: JORDAN1H:12

for A being finite Subset of REAL holds SgmX (RealOrd,A) is increasing

proof end;

theorem Th13: :: JORDAN1H:13

for f being FinSequence of REAL
for A being finite Subset of REAL st A = rng f holds
SgmX (RealOrd,A) = Incr f

proof end;

registration

let A be finite Subset of REAL;
cluster SgmX (RealOrd,A) -> increasing ;
coherence
SgmX (RealOrd,A) is increasing by Th12;

end;

theorem :: JORDAN1H:14

canceled;

theorem Th15: :: JORDAN1H:15

for X being non empty set
for A being finite Subset of X
for R being being_linear-order Order of X holds len (SgmX (R,A)) = card A

proof end;

begin

theorem Th16: :: JORDAN1H:16

for f being FinSequence of (TOP-REAL 2) holds X_axis f = proj1 * f

proof end;

theorem Th17: :: JORDAN1H:17

for f being FinSequence of (TOP-REAL 2) holds Y_axis f = proj2 * f

proof end;

definition

let D be non empty set ;
let M be FinSequence of D * ;
:: original: Values
redefine func Values M -> Subset of D;
coherence
Values M is Subset of D

proof end;

end;

registration

let D be non empty with_non-empty_elements set ;
let M be non empty non-empty FinSequence of D * ;
cluster Values M -> non empty ;
coherence
not Values M is empty

proof end;

end;

theorem Th18: :: JORDAN1H:18

for D being non empty set
for M being Matrix of D
for i being Element of NAT st i in Seg (width M) holds
rng (Col (M,i)) c= Values M

proof end;

theorem Th19: :: JORDAN1H:19

for D being non empty set
for M being Matrix of D
for i being Element of NAT st i in dom M holds
rng (Line (M,i)) c= Values M

proof end;

theorem Th20: :: JORDAN1H:20

for G being V21() X_increasing-in-column Matrix of (TOP-REAL 2) holds len G <= card (proj1 .: (Values G))

proof end;

theorem Th21: :: JORDAN1H:21

for G being X_equal-in-line Matrix of (TOP-REAL 2) holds card (proj1 .: (Values G)) <= len G

proof end;

theorem Th22: :: JORDAN1H:22

for G being V21() X_equal-in-line X_increasing-in-column Matrix of (TOP-REAL 2) holds len G = card (proj1 .: (Values G))

proof end;

theorem Th23: :: JORDAN1H:23

for G being V21() Y_increasing-in-line Matrix of (TOP-REAL 2) holds width G <= card (proj2 .: (Values G))

proof end;

theorem Th24: :: JORDAN1H:24

for G being V21() Y_equal-in-column Matrix of (TOP-REAL 2) holds card (proj2 .: (Values G)) <= width G

proof end;

theorem Th25: :: JORDAN1H:25

for G being V21() Y_equal-in-column Y_increasing-in-line Matrix of (TOP-REAL 2) holds width G = card (proj2 .: (Values G))

proof end;

begin

theorem :: JORDAN1H:26

for G being Go-board
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on G holds
for k being Element of NAT st 1 <= k & k + 1 <= len f holds
LSeg (f,k) c= left_cell (f,k,G)

proof end;

theorem :: JORDAN1H:27

for k being Element of NAT
for f being standard special_circular_sequence st 1 <= k & k + 1 <= len f holds
left_cell (f,k,(GoB f)) = left_cell (f,k)

proof end;

theorem Th28: :: JORDAN1H:28

for G being Go-board
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on G holds
for k being Element of NAT st 1 <= k & k + 1 <= len f holds
LSeg (f,k) c= right_cell (f,k,G)

proof end;

theorem Th29: :: JORDAN1H:29

for k being Element of NAT
for f being standard special_circular_sequence st 1 <= k & k + 1 <= len f holds
right_cell (f,k,(GoB f)) = right_cell (f,k)

proof end;

theorem :: JORDAN1H:30

for P being Subset of (TOP-REAL 2)
for f being non constant standard special_circular_sequence holds
( not P is_a_component_of (L~ f) ` or P = RightComp f or P = LeftComp f )

proof end;

theorem :: JORDAN1H:31

for G being Go-board
for f being non constant standard special_circular_sequence st f is_sequence_on G holds
for k being Element of NAT st 1 <= k & k + 1 <= len f holds
( Int (right_cell (f,k,G)) c= RightComp f & Int (left_cell (f,k,G)) c= LeftComp f )

proof end;

theorem Th32: :: JORDAN1H:32

for i1, j1, i2, j2 being Element of NAT
for G being Go-board st [i1,j1] in Indices G & [i2,j2] in Indices G & G * (i1,j1) = G * (i2,j2) holds
( i1 = i2 & j1 = j2 )

proof end;

theorem Th33: :: JORDAN1H:33

for i1, i2 being Element of NAT
for f being FinSequence of (TOP-REAL 2)
for M being Go-board st f is_sequence_on M holds
mid (f,i1,i2) is_sequence_on M

proof end;

registration

cluster non empty-yielding tabular X_equal-in-line Y_equal-in-column Y_increasing-in-line X_increasing-in-column -> non empty non-empty FinSequence of the carrier of (TOP-REAL 2) * ;
coherence
for b₁ being Go-board holds
( not b₁ is empty & b₁ is non-empty )

proof end;

end;

theorem Th34: :: JORDAN1H:34

for i being Element of NAT
for G being Go-board st 1 <= i & i <= len G holds
(SgmX (RealOrd,(proj1 .: (Values G)))) . i = (G * (i,1)) `1

proof end;

theorem Th35: :: JORDAN1H:35

for j being Element of NAT
for G being Go-board st 1 <= j & j <= width G holds
(SgmX (RealOrd,(proj2 .: (Values G)))) . j = (G * (1,j)) `2

proof end;

theorem Th36: :: JORDAN1H:36

for f being non empty FinSequence of (TOP-REAL 2)
for G being Go-board st f is_sequence_on G & ex i being Element of NAT st
( [1,i] in Indices G & G * (1,i) in rng f ) & ex i being Element of NAT st
( [(len G),i] in Indices G & G * ((len G),i) in rng f ) holds
proj1 .: (rng f) = proj1 .: (Values G)

proof end;

theorem Th37: :: JORDAN1H:37

for f being non empty FinSequence of (TOP-REAL 2)
for G being Go-board st f is_sequence_on G & ex i being Element of NAT st
( [i,1] in Indices G & G * (i,1) in rng f ) & ex i being Element of NAT st
( [i,(width G)] in Indices G & G * (i,(width G)) in rng f ) holds
proj2 .: (rng f) = proj2 .: (Values G)

proof end;

registration

let G be Go-board;
cluster Values G -> non empty ;
coherence
not Values G is empty

proof end;

end;

theorem Th38: :: JORDAN1H:38

for G being Go-board holds G = GoB ((SgmX (RealOrd,(proj1 .: (Values G)))),(SgmX (RealOrd,(proj2 .: (Values G)))))

proof end;

theorem Th39: :: JORDAN1H:39

for f being non empty FinSequence of (TOP-REAL 2)
for G being Go-board st proj1 .: (rng f) = proj1 .: (Values G) & proj2 .: (rng f) = proj2 .: (Values G) holds
G = GoB f

proof end;

theorem Th40: :: JORDAN1H:40

for f being non empty FinSequence of (TOP-REAL 2)
for G being Go-board st f is_sequence_on G & ex i being Element of NAT st
( [1,i] in Indices G & G * (1,i) in rng f ) & ex i being Element of NAT st
( [i,1] in Indices G & G * (i,1) in rng f ) & ex i being Element of NAT st
( [(len G),i] in Indices G & G * ((len G),i) in rng f ) & ex i being Element of NAT st
( [i,(width G)] in Indices G & G * (i,(width G)) in rng f ) holds
G = GoB f

proof end;

begin

theorem Th41: :: JORDAN1H:41

for i, n, m being Element of NAT st 1 <= i holds
[\(((i - 2) / (2 |^ (n -' m))) + 2)/] is Element of NAT

proof end;

theorem Th42: :: JORDAN1H:42

for m, n, i being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st m <= n & 1 <= i & i + 1 <= len (Gauge (C,n)) holds
( 1 <= [\(((i - 2) / (2 |^ (n -' m))) + 2)/] & [\(((i - 2) / (2 |^ (n -' m))) + 2)/] + 1 <= len (Gauge (C,m)) )

proof end;

theorem Th43: :: JORDAN1H:43

for m, n, i, j being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st m <= n & 1 <= i & i + 1 <= len (Gauge (C,n)) & 1 <= j & j + 1 <= width (Gauge (C,n)) holds
ex i1, j1 being Element of NAT st
( i1 = [\(((i - 2) / (2 |^ (n -' m))) + 2)/] & j1 = [\(((j - 2) / (2 |^ (n -' m))) + 2)/] & cell ((Gauge (C,n)),i,j) c= cell ((Gauge (C,m)),i1,j1) )

proof end;

theorem Th44: :: JORDAN1H:44

for m, n, i, j being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st m <= n & 1 <= i & i + 1 <= len (Gauge (C,n)) & 1 <= j & j + 1 <= width (Gauge (C,n)) holds
ex i1, j1 being Element of NAT st
( 1 <= i1 & i1 + 1 <= len (Gauge (C,m)) & 1 <= j1 & j1 + 1 <= width (Gauge (C,m)) & cell ((Gauge (C,n)),i,j) c= cell ((Gauge (C,m)),i1,j1) )

proof end;

theorem :: JORDAN1H:45

canceled;

theorem :: JORDAN1H:46

canceled;

theorem :: JORDAN1H:47

for P being Subset of (TOP-REAL 2) st P is Bounded holds
not UBD P is Bounded

proof end;

theorem Th48: :: JORDAN1H:48

for p being Point of (TOP-REAL 2)
for f being non constant standard special_circular_sequence st Rotate (f,p) is clockwise_oriented holds
f is clockwise_oriented

proof end;

theorem :: JORDAN1H:49

for f being non constant standard special_circular_sequence st LeftComp f = UBD (L~ f) holds
f is clockwise_oriented

proof end;

begin

theorem Th50: :: JORDAN1H:50

for f being non constant standard special_circular_sequence holds (Cl (LeftComp f)) ` = RightComp f

proof end;

theorem :: JORDAN1H:51

for f being non constant standard special_circular_sequence holds (Cl (RightComp f)) ` = LeftComp f

proof end;

theorem Th52: :: JORDAN1H:52

for n being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st C is connected holds
GoB (Cage (C,n)) = Gauge (C,n)

proof end;

theorem :: JORDAN1H:53

for n being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st C is connected holds
N-min C in right_cell ((Cage (C,n)),1)

proof end;

theorem Th54: :: JORDAN1H:54

for i, j being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st C is connected & i <= j holds
L~ (Cage (C,j)) c= Cl (RightComp (Cage (C,i)))

proof end;

theorem Th55: :: JORDAN1H:55

for i, j being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st C is connected & i <= j holds
LeftComp (Cage (C,i)) c= LeftComp (Cage (C,j))

proof end;

theorem :: JORDAN1H:56

for i, j being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st C is connected & i <= j holds
RightComp (Cage (C,j)) c= RightComp (Cage (C,i))

proof end;

begin

definition

let C be compact non horizontal non vertical Subset of (TOP-REAL 2);
let n be Element of NAT ;
func X-SpanStart (C,n) -> Element of NAT equals :: JORDAN1H:def 2
(2 |^ (n -' 1)) + 2;
correctness
coherence
(2 |^ (n -' 1)) + 2 is Element of NAT ;
;

end;

:: deftheorem defines X-SpanStart JORDAN1H:def 2 :
for C being compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT holds X-SpanStart (C,n) = (2 |^ (n -' 1)) + 2;

theorem :: JORDAN1H:57

canceled;

theorem Th58: :: JORDAN1H:58

for n being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) holds
( 2 < X-SpanStart (C,n) & X-SpanStart (C,n) < len (Gauge (C,n)) )

proof end;

theorem Th59: :: JORDAN1H:59

for n being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) holds
( 1 <= (X-SpanStart (C,n)) -' 1 & (X-SpanStart (C,n)) -' 1 < len (Gauge (C,n)) )

proof end;

definition

let C be compact non horizontal non vertical Subset of (TOP-REAL 2);
let n be Element of NAT ;
pred n is_sufficiently_large_for C means :Def3: :: JORDAN1H:def 3
ex j being Element of NAT st
( j < width (Gauge (C,n)) & cell ((Gauge (C,n)),((X-SpanStart (C,n)) -' 1),j) c= BDD C );

end;

:: deftheorem Def3 defines is_sufficiently_large_for JORDAN1H:def 3 :
for C being compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT holds
( n is_sufficiently_large_for C iff ex j being Element of NAT st
( j < width (Gauge (C,n)) & cell ((Gauge (C,n)),((X-SpanStart (C,n)) -' 1),j) c= BDD C ) );

theorem :: JORDAN1H:60

for n being Element of NAT
for C being compact non horizontal non vertical Subset of (TOP-REAL 2) st n is_sufficiently_large_for C holds
n >= 1

proof end;

theorem :: JORDAN1H:61

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j1 being Element of NAT st left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,j1) & [i1,(j1 + 1)] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i1,(j1 + 1)) holds
[(i1 -' 1),(j1 + 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:62

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j1 being Element of NAT st left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,j1) & [(i1 + 1),j1] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * ((i1 + 1),j1) holds
[(i1 + 1),(j1 + 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:63

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for j1, i2 being Element of NAT st left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [(i2 + 1),j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * ((i2 + 1),j1) & [i2,j1] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i2,j1) holds
[i2,(j1 -' 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:64

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j2 being Element of NAT st left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,(j2 + 1)] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,(j2 + 1)) & [i1,j2] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i1,j2) holds
[(i1 + 1),j2] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:65

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j1 being Element of NAT st front_left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,j1) & [i1,(j1 + 1)] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i1,(j1 + 1)) holds
[i1,(j1 + 2)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:66

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j1 being Element of NAT st front_left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,j1) & [(i1 + 1),j1] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * ((i1 + 1),j1) holds
[(i1 + 2),j1] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:67

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for j1, i2 being Element of NAT st front_left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [(i2 + 1),j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * ((i2 + 1),j1) & [i2,j1] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i2,j1) holds
[(i2 -' 1),j1] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:68

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j2 being Element of NAT st front_left_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,(j2 + 1)] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,(j2 + 1)) & [i1,j2] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i1,j2) holds
[i1,(j2 -' 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:69

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j1 being Element of NAT st front_right_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,j1) & [i1,(j1 + 1)] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i1,(j1 + 1)) holds
[(i1 + 1),(j1 + 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:70

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j1 being Element of NAT st front_right_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,j1) & [(i1 + 1),j1] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * ((i1 + 1),j1) holds
[(i1 + 1),(j1 -' 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:71

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for j1, i2 being Element of NAT st front_right_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [(i2 + 1),j1] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * ((i2 + 1),j1) & [i2,j1] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i2,j1) holds
[i2,(j1 + 1)] in Indices (Gauge (C,n))

proof end;

theorem :: JORDAN1H:72

for C being non empty compact non horizontal non vertical Subset of (TOP-REAL 2)
for n being Element of NAT
for f being FinSequence of (TOP-REAL 2) st f is_sequence_on Gauge (C,n) & len f > 1 holds
for i1, j2 being Element of NAT st front_right_cell (f,((len f) -' 1),(Gauge (C,n))) meets C & [i1,(j2 + 1)] in Indices (Gauge (C,n)) & f /. ((len f) -' 1) = (Gauge (C,n)) * (i1,(j2 + 1)) & [i1,j2] in Indices (Gauge (C,n)) & f /. (len f) = (Gauge (C,n)) * (i1,j2) holds
[(i1 -' 1),j2] in Indices (Gauge (C,n))

proof end;