Journal of Formalized Mathematics
Volume 3, 1991
University of Bialystok
Copyright (c) 1991 Association of Mizar Users

The abstract of the Mizar article:

The Topological Space $\calE^2_\rmT$. Arcs, Line Segments and Special Polygonal Arcs

by
Agata Darmochwal, and
Yatsuka Nakamura

Received November 21, 1991

MML identifier: TOPREAL1
[ Mizar article, MML identifier index ]


environ

 vocabulary EUCLID, METRIC_1, PCOMPS_1, BOOLE, FINSEQ_1, RELAT_1, FUNCT_1,
      PRE_TOPC, BORSUK_1, TOPS_2, RCOMP_1, SUBSET_1, MCART_1, ARYTM_1, ARYTM_3,
      CONNSP_2, TOPS_1, TOPMETR, COMPLEX1, ABSVALUE, ORDINAL2, COMPTS_1,
      TARSKI, SETFAM_1, TOPREAL1, FINSEQ_4, ARYTM;
 notation TARSKI, XBOOLE_0, SUBSET_1, ORDINAL1, ORDINAL2, NUMBERS, XREAL_0,
      REAL_1, NAT_1, RELAT_1, FUNCT_1, FUNCT_2, ABSVALUE, STRUCT_0, TOPS_1,
      TOPS_2, CONNSP_2, COMPTS_1, RCOMP_1, FINSEQ_1, FINSEQ_4, METRIC_1,
      TOPMETR, PCOMPS_1, EUCLID, PRE_TOPC;
 constructors REAL_1, NAT_1, ABSVALUE, TOPS_1, TOPS_2, COMPTS_1, RCOMP_1,
      EUCLID, TOPMETR, FINSEQ_4, INT_1, MEMBERED, XBOOLE_0, PRE_TOPC;
 clusters SUBSET_1, FUNCT_1, PRE_TOPC, RELSET_1, STRUCT_0, EUCLID, BORSUK_1,
      XREAL_0, METRIC_1, INT_1, TOPMETR, XBOOLE_0, NAT_1, MEMBERED, ZFMISC_1;
 requirements REAL, NUMERALS, BOOLE, SUBSET, ARITHM;


begin

reserve r,y1,y2,lambda for Real, i,j,n for Nat;
reserve a,m for natural number;

:: PRELIMINARIES

scheme Fraenkel_Alt {A() -> non empty set, P[set], Q[set]}:
 {v where v is Element of A(): P[v] or Q[v]} =
  {v1 where v1 is Element of A(): P[v1]} \/
   {v2 where v2 is Element of A(): Q[v2]};

reserve D for set, p for FinSequence of D;

definition let D, p, m;
 func p|m -> FinSequence of D equals
:: TOPREAL1:def 1
   p|Seg m;
end;

definition let D be set, f be FinSequence of D;
 cluster f|0 -> empty;
end;

theorem :: TOPREAL1:1
 a in dom(p|m) implies (p|m)/.a = p/.a;

theorem :: TOPREAL1:2
  len p <= m implies p|m = p;

theorem :: TOPREAL1:3
 m <= len p implies len(p|m) = m;

definition let T be 1-sorted;
 mode FinSequence of T is FinSequence of the carrier of T;
end;

:: PROPER TEXT

reserve p,p1,p2,q1,q2 for Point of TOP-REAL 2,
        P, P1 for Subset of TOP-REAL 2;

 definition let n;
    let p1, p2 be Point of TOP-REAL n,
        P be Subset of TOP-REAL n;
  pred P is_an_arc_of p1,p2 means
:: TOPREAL1:def 2
    ex f being map of I[01], (TOP-REAL n)|P st
                     f is_homeomorphism & f.0 = p1 & f.1 = p2;
 end;

theorem :: TOPREAL1:4
  for P being Subset of TOP-REAL n,
      p1,p2 being Point of TOP-REAL n
    st P is_an_arc_of p1,p2 holds p1 in P & p2 in P;

theorem :: TOPREAL1:5
  for P,Q being Subset of TOP-REAL n,
  p1,p2,q1 being Point of TOP-REAL n
   st P is_an_arc_of p1,p2 & Q is_an_arc_of p2,q1 & P /\ Q = {p2}
   holds P \/ Q is_an_arc_of p1,q1;

 definition
  func R^2-unit_square -> Subset of TOP-REAL 2 equals
:: TOPREAL1:def 3
    { p : p`1 = 0 & p`2 <= 1 & p`2 >= 0 or
                        p`1 <= 1 & p`1 >= 0 & p`2 = 1 or
                        p`1 <= 1 & p`1 >= 0 & p`2 = 0 or
                        p`1 = 1 & p`2 <= 1 & p`2 >= 0};
 end;

 definition let n; let p1,p2 be Point of TOP-REAL n;
   func LSeg(p1,p2) -> Subset of TOP-REAL n equals
:: TOPREAL1:def 4
 { (1-lambda)*p1 + lambda*p2 : 0 <= lambda & lambda <= 1 };
 end;

definition let n; let p1,p2 be Point of TOP-REAL n;
 cluster LSeg(p1,p2) -> non empty;
end;

theorem :: TOPREAL1:6
  for p1,p2 being Point of TOP-REAL n holds p1 in LSeg(p1,p2) & p2 in
 LSeg(p1,p2);

theorem :: TOPREAL1:7
  for p being Point of TOP-REAL n holds LSeg(p,p) = {p};

theorem :: TOPREAL1:8
  for p1,p2 being Point of TOP-REAL n holds LSeg(p1,p2) = LSeg(p2,p1);

 definition let n; let p1,p2 be Point of TOP-REAL n;
  redefine func LSeg(p1,p2); commutativity;
 end;

theorem :: TOPREAL1:9
 p1`1 <= p2`1 & p in LSeg(p1,p2) implies p1`1 <= p`1 & p`1 <= p2`1;

theorem :: TOPREAL1:10
 p1`2 <= p2`2 & p in LSeg(p1,p2) implies p1`2 <= p`2 & p`2 <= p2`2;

theorem :: TOPREAL1:11
 for p,p1,p2 being Point of TOP-REAL n st p in LSeg(p1,p2)
   holds LSeg(p1,p2) = LSeg(p1,p) \/ LSeg(p,p2);

theorem :: TOPREAL1:12
 for p1,p2,q1,q2 being Point of TOP-REAL n
    st q1 in LSeg(p1,p2) & q2 in LSeg(p1,p2) holds LSeg(q1,q2) c= LSeg(p1,p2);

theorem :: TOPREAL1:13
   for p,q,p1,p2 being Point of TOP-REAL n st p in LSeg(p1,p2) & q in LSeg(p1,
p2
)
  holds LSeg(p1,p2) = LSeg(p1,p) \/ LSeg(p,q) \/ LSeg(q,p2);

theorem :: TOPREAL1:14
   p in LSeg(p1,p2) implies LSeg(p1,p) /\ LSeg(p,p2) = {p};

theorem :: TOPREAL1:15
  for p1,p2 being Point of TOP-REAL n
   st p1 <> p2 holds LSeg(p1,p2) is_an_arc_of p1,p2;

theorem :: TOPREAL1:16
  for P being Subset of TOP-REAL n,
      p1,p2,q1 being Point of TOP-REAL n
   st P is_an_arc_of p1,p2 & P /\ LSeg(p2,q1) = {p2}
    holds P \/ LSeg(p2,q1) is_an_arc_of p1,q1;

theorem :: TOPREAL1:17
  for P being Subset of TOP-REAL n,
      p1,p2,q1 being Point of TOP-REAL n
   st P is_an_arc_of p2,p1 & LSeg(q1,p2) /\ P = {p2}
    holds LSeg(q1,p2) \/ P is_an_arc_of q1,p1;

theorem :: TOPREAL1:18
    for p1,p2,q1 being Point of TOP-REAL n
  st (p1 <> p2 or p2 <> q1) & LSeg(p1,p2) /\ LSeg(p2,q1) = {p2}
   holds LSeg(p1,p2) \/ LSeg(p2,q1) is_an_arc_of p1,q1;

theorem :: TOPREAL1:19
   LSeg(|[ 0,0 ]|, |[ 0,1 ]|) = { p1 : p1`1 = 0 & p1`2 <= 1 & p1`2 >= 0}
 & LSeg(|[ 0,1 ]|, |[ 1,1 ]|) = { p2 : p2`1 <= 1 & p2`1 >= 0 & p2`2 = 1}
 & LSeg(|[ 0,0 ]|, |[ 1,0 ]|) = { q1 : q1`1 <= 1 & q1`1 >= 0 & q1`2 = 0}
 & LSeg(|[ 1,0 ]|, |[ 1,1 ]|) = { q2 : q2`1 = 1 & q2`2 <= 1 & q2`2 >= 0};

theorem :: TOPREAL1:20
 R^2-unit_square = (LSeg(|[ 0,0 ]|, |[ 0,1 ]|) \/ LSeg(|[ 0,1 ]|, |[ 1,1 ]|))
 \/ (LSeg(|[ 0,0 ]|, |[ 1,0 ]|) \/ LSeg(|[ 1,0 ]|, |[ 1,1 ]|));

definition
 cluster R^2-unit_square -> non empty;
end;

theorem :: TOPREAL1:21
   LSeg(|[0,0]|,|[0,1]|) /\ LSeg(|[0,1]|,|[1,1]|) = {|[0,1]|};

theorem :: TOPREAL1:22
   LSeg(|[0,0]|,|[1,0]|) /\ LSeg(|[1,0]|,|[1,1]|) = {|[1,0]|};

theorem :: TOPREAL1:23
 LSeg(|[0,0]|,|[0,1]|) /\ LSeg(|[0,0]|,|[1,0]|) = {|[0,0]|};

theorem :: TOPREAL1:24
 LSeg(|[0,1]|,|[1,1]|) /\ LSeg(|[1,0]|,|[1,1]|) = {|[1,1]|};

theorem :: TOPREAL1:25
   LSeg(|[0,0]|,|[1,0]|) misses LSeg(|[0,1]|,|[1,1]|);

theorem :: TOPREAL1:26
 LSeg(|[0,0]|,|[0,1]|) misses LSeg(|[1,0]|,|[1,1]|);

definition let n; let f be FinSequence of TOP-REAL n; let i;
 func LSeg(f,i) -> Subset of TOP-REAL n equals
:: TOPREAL1:def 5
 LSeg(f/.i,f/.(i+1)) if 1 <= i & i+1 <= len f
         otherwise {};
end;

theorem :: TOPREAL1:27
 for f being FinSequence of TOP-REAL n st 1 <= i & i+1 <= len f
  holds f/.i in LSeg(f,i) & f/.(i+1) in LSeg(f,i);

definition let n; let f be FinSequence of TOP-REAL n;
 func L~f -> Subset of TOP-REAL n equals
:: TOPREAL1:def 6
   union { LSeg(f,i) : 1 <= i & i+1 <= len f };
end;

theorem :: TOPREAL1:28
 for f being FinSequence of TOP-REAL n
  holds (len f = 0 or len f = 1) iff L~f = {};

theorem :: TOPREAL1:29
 for f being FinSequence of TOP-REAL n holds len f >= 2 implies L~f <> {};

definition let IT be FinSequence of TOP-REAL 2;
 attr IT is special means
:: TOPREAL1:def 7
    for i st 1 <= i & i+1 <= len IT holds
    (IT/.i)`1 = (IT/.(i+1))`1 or (IT/.i)`2 = (IT/.(i+1))`2;
 attr IT is unfolded means
:: TOPREAL1:def 8
  for i st 1 <= i & i + 2 <= len IT
       holds LSeg(IT,i) /\ LSeg(IT,i+1) = {IT/.(i+1)};
 attr IT is s.n.c. means
:: TOPREAL1:def 9
 for i,j st i+1 < j holds LSeg(IT,i) misses LSeg(IT,j);
end;

reserve f,f1,f2,h for FinSequence of TOP-REAL 2;

definition let f;
 attr f is being_S-Seq means
:: TOPREAL1:def 10
  f is one-to-one & len f >= 2 & f is unfolded s.n.c. special;
  synonym f is_S-Seq;
end;

theorem :: TOPREAL1:30
 ex f1,f2 st f1 is_S-Seq & f2 is_S-Seq & R^2-unit_square = L~f1 \/ L~f2 &
  L~f1 /\ L~f2 = {|[ 0,0 ]|, |[ 1,1 ]|} & f1/.1 = |[0,0]| &
  f1/.len f1=|[1,1]| & f2/.1 = |[0,0]| & f2/.len f2 = |[1,1]|;

theorem :: TOPREAL1:31
 h is_S-Seq implies L~h is_an_arc_of h/.1,h/.len h;

 definition let P be Subset of TOP-REAL 2;
  attr P is being_S-P_arc means
:: TOPREAL1:def 11

   ex f st f is_S-Seq & P = L~f;
  synonym P is_S-P_arc;
 end;

theorem :: TOPREAL1:32
P1 is_S-P_arc implies P1 <> {};

 definition
  cluster being_S-P_arc -> non empty Subset of TOP-REAL 2;
 end;

canceled;

theorem :: TOPREAL1:34
   ex P1, P2 being non empty Subset of TOP-REAL 2
  st P1 is_S-P_arc & P2 is_S-P_arc & R^2-unit_square = P1 \/ P2 &
   P1 /\ P2 = {|[ 0,0 ]|, |[ 1,1 ]|};

theorem :: TOPREAL1:35
P is_S-P_arc implies ex p1,p2 st P is_an_arc_of p1,p2;

theorem :: TOPREAL1:36
   P is_S-P_arc implies
  ex f being map of I[01], (TOP-REAL 2)|P st f is_homeomorphism;

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