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<b>let </b><font color="Maroon" title="c1">C</font> be   <a href="topreal2.html#NM1" title="TOPREAL2:NM.1">Simple_closed_curve</a>;<br/><b>let </b><font color="Maroon" title="c2">S</font> be    <a href="jordan_a.html#M1" title="JORDAN_A:mode.1">Segmentation</a> of <font color="Maroon" title="c1">C</font>;<br/><b>let </b><font color="Maroon" title="c3">i</font>, <font color="Maroon" title="c4">j</font> be    <a href="subset_1.html#M2" title="SUBSET_1:mode.2">Element</a> of  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a> ;<br/>







<b>assume </b><b>that </b><br/><a NAME="E1:34"/><i><font color="Green" title="E27">A1</font></i>: 
1 <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon" title="c3">i</font>
 <b>and </b><br/><a NAME="E2:34"/><i><font color="Green" title="E28">A2</font></i>: 
<font color="Maroon" title="c3">i</font> <a href="xxreal_0.html#NR3" title="XXREAL_0:NR.3">&lt;</a> <font color="Maroon" title="c4">j</font>
 <b>and </b><br/><a NAME="E3:34"/><i><font color="Green" title="E29">A3</font></i>: 
<font color="Maroon" title="c4">j</font> <a href="xxreal_0.html#NR3" title="XXREAL_0:NR.3">&lt;</a>  <a href="finseq_1.html#K3" title="FINSEQ_1:func.3">len</a> <font color="Maroon" title="c2">S</font>
 <b>and </b><br/><a NAME="E4:34"/><i><font color="Green" title="E30">A4</font></i>: 
<font color="Maroon" title="c3">i</font>,<font color="Maroon" title="c4">j</font> <a href="gobrd10.html#R1" title="GOBRD10:pred.1">are_adjacent1</a> 
 ;<br/>

<a NAME="E5:34"/>
<font color="Maroon" title="c3">i</font> <a href="xxreal_0.html#NR3" title="XXREAL_0:NR.3">&lt;</a>  <a href="finseq_1.html#K3" title="FINSEQ_1:func.3">len</a> <font color="Maroon" title="c2">S</font>
 
<b>by </b><i><a class="txt" href="jordan_a.html#E2:34"><i><font color="Green" title="E28">A2</font></i></a>, <a class="txt" href="jordan_a.html#E3:34"><i><font color="Green" title="E29">A3</font></i></a>, <a class="ref" href="xxreal_0.html#T2" title="XXREAL_0:th.2">XXREAL_0:2</a></i>;<br/>
<a NAME="E6:34"/><b>then </b><i><font color="Green" title="E31">A5</font></i>: 
 <a href="jordan_a.html#K2" title="JORDAN_A:func.2">Segm</a> <font color="Maroon" title="c2">S</font>,<font color="Maroon" title="c3">i</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="jordan7.html#K1" title="JORDAN7:func.1">Segment</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">S</font> <a href="finseq_4.html#K4" title="FINSEQ_4:func.4">/.</a> <font color="Maroon" title="c3">i</font></span>)</span>,<span class="p1">(<span class="default"><font color="Maroon" title="c2">S</font> <a href="finseq_4.html#K4" title="FINSEQ_4:func.4">/.</a> <span class="p2">(<span class="default"><font color="Maroon" title="c3">i</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1</span>)</span></span>)</span>,<font color="Maroon" title="c1">C</font>
 
<b>by </b><i><a class="txt" href="jordan_a.html#E1:34"><i><font color="Green" title="E27">A1</font></i></a>, <a class="ref" href="jordan_a.html#D4" target="_self" title="JORDAN_A:def.4">Def4</a></i>;<br/>
<a NAME="E7:34"/>
1 <a href="xxreal_0.html#NR3" title="XXREAL_0:NR.3">&lt;</a> <font color="Maroon" title="c4">j</font>
 
<b>by </b><i><a class="txt" href="jordan_a.html#E1:34"><i><font color="Green" title="E27">A1</font></i></a>, <a class="txt" href="jordan_a.html#E2:34"><i><font color="Green" title="E28">A2</font></i></a>, <a class="ref" href="xxreal_0.html#T2" title="XXREAL_0:th.2">XXREAL_0:2</a></i>;<br/>
<a NAME="E8:34"/><b>then </b><i><font color="Green" title="E32">A6</font></i>: 
 <a href="jordan_a.html#K2" title="JORDAN_A:func.2">Segm</a> <font color="Maroon" title="c2">S</font>,<font color="Maroon" title="c4">j</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="jordan7.html#K1" title="JORDAN7:func.1">Segment</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">S</font> <a href="finseq_4.html#K4" title="FINSEQ_4:func.4">/.</a> <font color="Maroon" title="c4">j</font></span>)</span>,<span class="p1">(<span class="default"><font color="Maroon" title="c2">S</font> <a href="finseq_4.html#K4" title="FINSEQ_4:func.4">/.</a> <span class="p2">(<span class="default"><font color="Maroon" title="c4">j</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1</span>)</span></span>)</span>,<font color="Maroon" title="c1">C</font>
 
<b>by </b><i><a class="txt" href="jordan_a.html#E3:34"><i><font color="Green" title="E29">A3</font></i></a>, <a class="ref" href="jordan_a.html#D4" target="_self" title="JORDAN_A:def.4">Def4</a></i>;<br/>
<a NAME="E9:34"/>
<font color="Maroon" title="c4">j</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1 <a href="xxreal_0.html#NR4" title="XXREAL_0:NR.4">&gt;</a> <font color="Maroon" title="c3">i</font>
 
<b>by </b><i><a class="txt" href="jordan_a.html#E2:34"><i><font color="Green" title="E28">A2</font></i></a>, <a class="ref" href="nat_1.html#T13" title="NAT_1:th.13">NAT_1:13</a></i>;<br/>
<a NAME="E10:34"/><b>then </b>
<font color="Maroon" title="c4">j</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c3">i</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1
 
<b>by </b><i><a class="txt" href="jordan_a.html#E4:34"><i><font color="Green" title="E30">A4</font></i></a>, <a class="ref" href="gobrd10.html#D1" title="GOBRD10:def.1">GOBRD10:def 1</a></i>;<br/>
<a NAME="E11:34"/><b>then </b>
<font color="Maroon" title="c4">j</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1 <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c3">i</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> <span class="p1">(<span class="default">1 <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1</span>)</span>
 
;<br/>
<b>hence </b><a NAME="E12:34"/>
<span class="p1">(<span class="default"><a href="jordan_a.html#K2" title="JORDAN_A:func.2">Segm</a> <font color="Maroon" title="c2">S</font>,<font color="Maroon" title="c3">i</font></span>)</span> <a href="subset_1.html#K9" title="SUBSET_1:func.9">/\</a> <span class="p1">(<span class="default"><a href="jordan_a.html#K2" title="JORDAN_A:func.2">Segm</a> <font color="Maroon" title="c2">S</font>,<font color="Maroon" title="c4">j</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1"><a href="domain_1.html#K6" title="DOMAIN_1:func.6">{</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c2">S</font> <a href="finseq_4.html#K4" title="FINSEQ_4:func.4">/.</a> <span class="p3">(<span class="default"><font color="Maroon" title="c3">i</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1</span>)</span></span>)</span></span><a href="domain_1.html#K6" title="DOMAIN_1:func.6">}</a></span>
 <b>by </b><i><a class="txt" href="jordan_a.html#E1:34"><i><font color="Green" title="E27">A1</font></i></a>, <a class="txt" href="jordan_a.html#E3:34"><i><font color="Green" title="E29">A3</font></i></a>, <a class="txt" href="jordan_a.html#E6:34"><i><font color="Green" title="E31">A5</font></i></a>, <a class="txt" href="jordan_a.html#E8:34"><i><font color="Green" title="E32">A6</font></i></a>, <a class="ref" href="jordan_a.html#D3" target="_self" title="JORDAN_A:def.3">Def3</a></i>;<br/>


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