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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="glib_000.html#NM2">_Graph</a>;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be    <a href="glib_000.html#M2">Subgraph</a> of <font color="Maroon">c<sub>1</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font> be    <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>2</sub></font>;<br/>





<b>reconsider </b><font color="Maroon">c<sub>4</sub></font> = <font color="Maroon">c<sub>3</sub></font> as    <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font> <b>by </b><i><a class="ref" href="glib_001.html#T168" target="_self">Th168</a></i>;<br/>
<div><b>hereby </b>
<div class="add"><b>assume </b><a NAME="E1:246_1"/>
<font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V1" target="_self">closed</a>
 ;<br/><a NAME="E2:246_1"/><b>then </b>
<font color="Maroon">c<sub>3</sub></font> <a href="glib_001.html#K3" target="_self">.first()</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>3</sub></font> <a href="glib_001.html#K4" target="_self">.last()</a> 
 <b>by </b><i><a class="ref" href="glib_001.html#D24" target="_self">Def24</a></i>;<br/><b>then </b><font color="Maroon">c<sub>3</sub></font> <a href="funct_1.html#K1">.</a> 1 = 
<font color="Maroon">c<sub>3</sub></font> <a href="glib_001.html#K4" target="_self">.last()</a> 

<br/>.= 
<font color="Maroon">c<sub>3</sub></font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>

;<br/><a NAME="E4:246_1"/><b>then </b>
<font color="Maroon">c<sub>4</sub></font> <a href="glib_001.html#K3" target="_self">.first()</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font></span>)</span>
 ;<br/><a NAME="E5:246_1"/><b>then </b>
<font color="Maroon">c<sub>4</sub></font> <a href="glib_001.html#K3" target="_self">.first()</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="glib_001.html#K4" target="_self">.last()</a> 
 ;<br/><b>hence </b><a NAME="E6:246_1"/>
<font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V1" target="_self">closed</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="ref" href="glib_001.html#D24" target="_self">Def24</a></i>;<br/></div>
<b>end;</b></div>

<div><b>hereby </b>
<div class="add"><b>assume </b><a NAME="E1:246_2"/><i><font color="Green">E160</font></i>: 
<font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V2" target="_self">directed</a>
 ;<br/><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="246_2_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">c<sub>5</sub></font> be  <a href="abian.html#V1">odd</a> <a href="nat_1.html#NM1">Nat</a>;<br/><b>assume </b><a NAME="E1:246_2_1"/><i><font color="Green">E161</font></i>: 
<font color="Maroon">c<sub>5</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font>
 ;<br/><a NAME="E2:246_2_1"/><b>then </b><i><font color="Green">E162</font></i>: 
<span class="p1">(<span class="default"><a href="glib_000.html#K10">the_Source_of</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><font color="Maroon">c<sub>5</sub></font> <a href="nat_1.html#K1">+</a> 1</span>)</span></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Maroon">c<sub>5</sub></font>
 <b>by </b><i><a class="txt" href="glib_001.html#E1:246_2"><i><font color="Green">E160</font></i></a>, <a class="ref" href="glib_001.html#D25" target="_self">Def25</a></i>;<br/><a NAME="E3:246_2_1"/><i><font color="Green">E163</font></i>: 
1 <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">c<sub>5</sub></font> <a href="nat_1.html#K1">+</a> 1
 <b>by </b><i><a class="ref" href="nat_1.html#T37">NAT_1:37</a></i>;<br/><a NAME="E4:246_2_1"/>
<font color="Maroon">c<sub>5</sub></font> <a href="nat_1.html#K1">+</a> 1 <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font>
 <b>by </b><i><a class="txt" href="glib_001.html#E1:246_2_1"><i><font color="Green">E161</font></i></a>, <a class="ref" href="nat_1.html#T38">NAT_1:38</a></i>;<br/><a NAME="E5:246_2_1"/><b>then </b>
<font color="Maroon">c<sub>5</sub></font> <a href="nat_1.html#K1">+</a> 1 <a href="hidden.html#R2">in</a>  <a href="relset_1.html#K4">dom</a> <font color="Maroon">c<sub>4</sub></font>
 <b>by </b><i><a class="txt" href="glib_001.html#E3:246_2_1"><i><font color="Green">E163</font></i></a>, <a class="ref" href="finseq_3.html#T27">FINSEQ_3:27</a></i>;<br/><a NAME="E6:246_2_1"/><b>then </b>
<font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>5</sub></font> <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="hidden.html#R2">in</a>  <a href="glib_000.html#K26">the_Edges_of</a> <font color="Maroon">c<sub>2</sub></font>
 <b>by </b><i><a class="ref" href="glib_001.html#T9" target="_self">Th9</a></i>;<br/><b>hence </b><a NAME="E7:246_2_1"/>
<span class="p1">(<span class="default"><a href="glib_000.html#K10">the_Source_of</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><font color="Maroon">c<sub>5</sub></font> <a href="nat_1.html#K1">+</a> 1</span>)</span></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Maroon">c<sub>5</sub></font>
 <b>by </b><i><a class="ref" href="glib_000.html#D34">GLIB_000:def 34</a>, <a class="txt" href="glib_001.html#E2:246_2_1"><i><font color="Green">E162</font></i></a></i>;<br/></div><b>end;</b></div><b>hence </b><a NAME="E3:246_2"/>
<font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V2" target="_self">directed</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="ref" href="glib_001.html#D25" target="_self">Def25</a></i>;<br/></div>
<b>end;</b></div>

<div><b>hereby </b>
<div class="add"><b>assume </b><a NAME="E1:246_3"/>
<font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V3" target="_self">trivial</a>
 ;<br/><a NAME="E2:246_3"/><b>then </b>
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#R1">=</a> 1
 <b>by </b><i><a class="txt" href="glib_001.html#E97"><i><font color="Green">Lemma89</font></i></a></i>;<br/><b>hence </b><a NAME="E3:246_3"/>
<font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V3" target="_self">trivial</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="txt" href="glib_001.html#E96"><i><font color="Green">Lemma88</font></i></a></i>;<br/></div>
<b>end;</b></div>

<div><i><font color="Green">E160</font></i>: <a class="txt" onclick="hs2(this)" href="javascript:()" title="246_4"><b>now </b></a><div class="add"><b>assume </b><a NAME="E1:246_4"/>
<font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V4" target="_self">Trail-like</a>
 ;<br/><a NAME="E2:246_4"/><b>then </b>
for <font color="Olive">b<sub>1</sub></font>, <font color="Olive">b<sub>2</sub></font> being <a href="abian.html#V1">even</a> <a href="nat_1.html#NM1">Nat</a> st 1 <a href="xxreal_0.html#R1">&lt;=</a> <font color="Olive">b<sub>1</sub></font> &amp; <font color="Olive">b<sub>1</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Olive">b<sub>2</sub></font> &amp; <font color="Olive">b<sub>2</sub></font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>3</sub></font> holds <br/><font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Olive">b<sub>2</sub></font>
 <b>by </b><i><a class="txt" href="glib_001.html#E99"><i><font color="Green">Lemma91</font></i></a></i>;<br/><b>hence </b><a NAME="E3:246_4"/>
<font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V4" target="_self">Trail-like</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="txt" href="glib_001.html#E99"><i><font color="Green">Lemma91</font></i></a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E6:246"/>
( <font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V4" target="_self">Trail-like</a> implies <font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V4" target="_self">Trail-like</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font> )
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="246_5"><b>now </b></a><div class="add"><b>assume </b><a NAME="E1:246_5"/>
<font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V5" target="_self">Path-like</a>
 ;<br/><a NAME="E2:246_5"/><b>then </b>
( <font color="Maroon">c<sub>4</sub></font> is <a href="glib_001.html#V4" target="_self">Trail-like</a> &amp; ( for <font color="Olive">b<sub>1</sub></font>, <font color="Olive">b<sub>2</sub></font> being <a href="abian.html#V1">odd</a> <a href="nat_1.html#NM1">Nat</a> st <font color="Olive">b<sub>1</sub></font> <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Olive">b<sub>2</sub></font> &amp; <font color="Olive">b<sub>2</sub></font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font> &amp; <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Olive">b<sub>2</sub></font> holds <br/>( <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> 1 &amp; <font color="Olive">b<sub>2</sub></font> <a href="hidden.html#R1">=</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font> ) ) )
 <b>by </b><i><a class="txt" href="glib_001.html#E5:246"><i><font color="Green">E160</font></i></a>, <a class="ref" href="glib_001.html#D28" target="_self">Def28</a></i>;<br/><b>hence </b><a NAME="E3:246_5"/>
<font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V5" target="_self">Path-like</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="ref" href="glib_001.html#D28" target="_self">Def28</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E8:246"/>
( <font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V5" target="_self">Path-like</a> implies <font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V5" target="_self">Path-like</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font> )
 ;<br/>

<div><b>hereby </b>
<div class="add"><b>assume </b><a NAME="E1:246_6"/>
<font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V6" target="_self">vertex-distinct</a>
 ;<br/><a NAME="E2:246_6"/><b>then </b>
for <font color="Olive">b<sub>1</sub></font>, <font color="Olive">b<sub>2</sub></font> being <a href="abian.html#V1">odd</a> <a href="nat_1.html#NM1">Nat</a> st <font color="Olive">b<sub>1</sub></font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font> &amp; <font color="Olive">b<sub>2</sub></font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>4</sub></font> &amp; <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="funct_1.html#K1">.</a> <font color="Olive">b<sub>2</sub></font> holds <br/><font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Olive">b<sub>2</sub></font>
 <b>by </b><i><a class="ref" href="glib_001.html#D29" target="_self">Def29</a></i>;<br/><b>hence </b><a NAME="E3:246_6"/>
<font color="Maroon">c<sub>3</sub></font> is  <a href="glib_001.html#V6" target="_self">vertex-distinct</a>  <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="ref" href="glib_001.html#D29" target="_self">Def29</a></i>;<br/></div>
<b>end;</b></div>

<b>thus </b><a NAME="E10:246"/>
verum
 ;<br/>


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