<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">e</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">V</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">G</font> be  <a href="graph_1.html#V3">oriented</a> <a href="graph_1.html#V7">finite</a> <a href="graph_1.html#NM1">Graph</a>;<br/><b>let </b><font color="Maroon">P</font> be  <a href="graph_1.html#V8">oriented</a>  <a href="graph_1.html#M2">Chain</a> of <font color="Maroon">G</font>;<br/><b>let </b><font color="Maroon">Q</font> be  <a href="graph_1.html#V8">oriented</a>  <a href="graph_1.html#M2">Chain</a> of <font color="Maroon">G</font>;<br/><b>let </b><font color="Maroon">W</font> be   <a href="funct_2.html#NM1">Function</a> of the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font>, <a href="graph_5.html#K8">Real&gt;=0</a> ;<br/><b>let </b><font color="Maroon">v1</font> be   <a href="graph_3.html#NM2">Vertex</a> of <font color="Maroon">G</font>;<br/><b>let </b><font color="Maroon">v2</font> be   <a href="graph_3.html#NM2">Vertex</a> of <font color="Maroon">G</font>;<br/><b>let </b><font color="Maroon">v3</font> be   <a href="graph_3.html#NM2">Vertex</a> of <font color="Maroon">G</font>;<br/>

















<b>assume </b><a NAME="E1:19"/><i><font color="Green">E34</font></i>: 
( <font color="Maroon">e</font> <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font> &amp; <font color="Maroon">P</font> <a href="graph_5.html#R8">is_shortestpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v2</font>,<font color="Maroon">V</font>,<font color="Maroon">W</font> &amp; <font color="Maroon">v1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">v3</font> &amp; <font color="Maroon">Q</font> <a href="hidden.html#R1">=</a> <font color="Maroon">P</font> <a href="finseq_1.html#K7">^</a> <span class="p1"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><font color="Maroon">e</font></span><a href="finseq_1.html#K9">*&gt;</a></span> &amp; <font color="Maroon">e</font> <a href="graph_4.html#R1">orientedly_joins</a> <font color="Maroon">v2</font>,<font color="Maroon">v3</font> &amp; <font color="Maroon">v1</font> <a href="hidden.html#R2">in</a> <font color="Maroon">V</font> &amp; ( for <font color="Olive">v4</font> being  <a href="graph_3.html#NM2">Vertex</a> of <font color="Maroon">G</font>  st <font color="Olive">v4</font> <a href="hidden.html#R2">in</a> <font color="Maroon">V</font> holds <br/>for <font color="Olive">ee</font> being   <a href="hidden.html#M1">set</a>   holds <br/>(  not <font color="Olive">ee</font> <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font> or  not <font color="Olive">ee</font> <a href="graph_4.html#R1">orientedly_joins</a> <font color="Olive">v4</font>,<font color="Maroon">v3</font> ) ) )
 ;<br/>

<b>set </b><font color="Maroon">V'</font> = <font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>;<br/>
<b>set </b><font color="Maroon">FS</font> = the <a href="graph_1.html#U3">Source</a> of <font color="Maroon">G</font>;<br/>
<b>set </b><font color="Maroon">FT</font> = the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font>;<br/>
<a NAME="E2:19"/><i><font color="Green">E52</font></i>: 
<font color="Maroon">W</font> <a href="graph_5.html#R5">is_weight&gt;=0of</a> <font color="Maroon">G</font>
 
<b>by </b><i><a class="ref" href="graph_5.html#D13">GRAPH_5:def 13</a></i>;<br/>
<a NAME="E3:19"/><b>then </b><i><font color="Green">E53</font></i>: 
<font color="Maroon">W</font> <a href="graph_5.html#R6">is_weight_of</a> <font color="Maroon">G</font>
 
<b>by </b><i><a class="ref" href="graph_5.html#T50">GRAPH_5:50</a></i>;<br/>
<b>set </b><font color="Maroon">Eg</font> = the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font>;<br/>
<div><i><font color="Green">E54</font></i>: <a class="txt" onclick="hs2(this)" href="javascript:()" title="19_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">S</font> be  <a href="graph_1.html#V8">oriented</a>  <a href="graph_1.html#M2">Chain</a> of <font color="Maroon">G</font>;<br/><b>assume </b><a NAME="E1:19_1"/><i><font color="Green">E62</font></i>: 
<font color="Maroon">S</font> <a href="graph_5.html#R2">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>,<font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 ;<br/><b>then consider </b><font color="Maroon">s</font> being  <a href="graph_1.html#V8">oriented</a> <a href="graph_4.html#V1">Simple</a>  <a href="graph_1.html#M2">Chain</a> of <font color="Maroon">G</font><b> such that </b><br/><a NAME="E3:19_1"/><i><font color="Green">E63</font></i>: 
<font color="Maroon">s</font> <a href="graph_5.html#R8">is_shortestpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>,<font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>,<font color="Maroon">W</font>
 <b>by </b><i>, <a class="ref" href="graph_5.html#T66">GRAPH_5:66</a></i>;<br/><a NAME="E4:19_1"/><i><font color="Green">E64</font></i>: 
<font color="Maroon">s</font> <a href="graph_5.html#R2">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>,<font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, <a class="ref" href="graph_5.html#D18">GRAPH_5:def 18</a></i>;<br/><a NAME="E5:19_1"/><b>then </b><i><font color="Green">E65</font></i>: 
<font color="Maroon">s</font> <a href="graph_5.html#R1">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>
 <b>by </b><i><a class="ref" href="graph_5.html#D4">GRAPH_5:def 4</a></i>;<br/><a NAME="E6:19_1"/><b>then </b>
<font color="Maroon">s</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 <b>by </b><i><a class="ref" href="graph_5.html#D3">GRAPH_5:def 3</a></i>;<br/><a NAME="E7:19_1"/><b>then </b><i><font color="Green">E66</font></i>: 
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1
 <b>by </b><i><a class="ref" href="graph_5.html#T8">GRAPH_5:8</a></i>;<br/><b>then consider </b><font color="Maroon">i</font> being   <a href="nat_1.html#NM1">Nat</a><b> such that </b><br/><a NAME="E9:19_1"/><i><font color="Green">E67</font></i>: 
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font> <a href="hidden.html#R1">=</a> 1 <a href="xcmplx_0.html#K2">+</a> <font color="Maroon">i</font>
 <b>by </b><i><a class="ref" href="nat_1.html#T28">NAT_1:28</a></i>;<br/><a NAME="E10:19_1"/>
<font color="Maroon">i</font> <a href="hidden.html#R2">in</a>  <a href="numbers.html#K5">NAT</a> 
 <b>by </b><i><a class="ref" href="ordinal1.html#D13">ORDINAL1:def 13</a></i>;<br/><b>then consider </b><font color="Maroon">s1</font> being   <a href="finseq_1.html#NM1">FinSequence</a>, <font color="Maroon">s2</font> being   <a href="finseq_1.html#NM1">FinSequence</a><b> such that </b><br/><a NAME="E12:19_1"/><i><font color="Green">E68</font></i>: 
(  <a href="finseq_1.html#K3">len</a> <font color="Maroon">s1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">i</font> &amp;  <a href="finseq_1.html#K3">len</a> <font color="Maroon">s2</font> <a href="hidden.html#R1">=</a> 1 &amp; <font color="Maroon">s</font> <a href="hidden.html#R1">=</a> <font color="Maroon">s1</font> <a href="finseq_1.html#K7">^</a> <font color="Maroon">s2</font> )
 <b>by </b><i>, <a class="ref" href="finseq_2.html#T25">FINSEQ_2:25</a></i>;<br/><b>reconsider </b><font color="Maroon">s1</font> = <font color="Maroon">s1</font>, <font color="Maroon">s2</font> = <font color="Maroon">s2</font> as  <a href="graph_1.html#V8">oriented</a> <a href="graph_4.html#V1">Simple</a>  <a href="graph_1.html#M2">Chain</a> of <font color="Maroon">G</font> <b>by </b><i>, <a class="ref" href="graph_5.html#T17">GRAPH_5:17</a></i>;<br/><a NAME="E14:19_1"/><i><font color="Green">E69</font></i>: 
<font color="Maroon">s2</font> <a href="funct_1.html#K1">.</a> 1 <a href="hidden.html#R1">=</a> <font color="Maroon">s</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">s</font></span>)</span>
 <b>by </b><i>, , </i>;<br/><a NAME="E15:19_1"/><i><font color="Green">E70</font></i>: 
( the <a href="graph_1.html#U3">Source</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> 1</span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">v1</font> &amp; the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">v3</font> )
 <b>by </b><i>, <a class="ref" href="graph_5.html#D3">GRAPH_5:def 3</a></i>;<br/><b>reconsider </b><font color="Maroon">vx</font> = the <a href="graph_1.html#U3">Source</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s2</font> <a href="funct_1.html#K1">.</a> 1</span>)</span> as   <a href="graph_3.html#NM2">Vertex</a> of <font color="Maroon">G</font> <b>by </b><i>, </i>;<br/><a NAME="E17:19_1"/><i><font color="Green">E71</font></i>: 
<font color="Maroon">s1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="19_1_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:19_1_1"/>
<font color="Maroon">s1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<a NAME="E2:19_1_1"/><b>then </b><i><font color="Green">E84</font></i>: 
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font> <a href="hidden.html#R1">=</a> 1 <a href="nat_1.html#K1">+</a> 0
 
<b>by </b><i>, , <a class="ref" href="finseq_1.html#T25">FINSEQ_1:25</a></i>;<br/>
<a NAME="E3:19_1_1"/><b>then </b><i><font color="Green">E86</font></i>: 
<font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> 1 <a href="graph_4.html#R1">orientedly_joins</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>
 
<b>by </b><i>, <a class="ref" href="graph_4.html#D1">GRAPH_4:def 1</a></i>;<br/>
<a NAME="E4:19_1_1"/>
<font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> 1 <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font>
 
<b>by </b><i><a class="txt" href="graphsp.html#E1:19"><i><font color="Green">E34</font></i></a>, </i>;<br/>
<b>hence </b><a NAME="E5:19_1_1"/>
contradiction
 <b>by </b><i>, <a class="ref" href="graphsp.html#T2" target="_self">Th2</a></i>;<br/>


</div><b>end;</b></div><a NAME="E18:19_1"/><b>then </b><i><font color="Green">E98</font></i>: 
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">s1</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1
 <b>by </b><i><a class="ref" href="graph_5.html#T8">GRAPH_5:8</a></i>;<br/><a NAME="E19:19_1"/>
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">s1</font> <a href="xxreal_0.html#R1">&lt;</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font>
 <b>by </b><i>, , <a class="ref" href="nat_1.html#T38">NAT_1:38</a></i>;<br/><b>then </b><i><font color="Green">E99</font></i>: the <a href="graph_1.html#U3">Source</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font></span>)</span></span>)</span> = 
the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">s1</font></span>)</span></span>)</span>
<b>by </b><i>, , <a class="txt" href="graphsp.html#E1:19"><i><font color="Green">E34</font></i></a>, <a class="ref" href="graph_1.html#D12">GRAPH_1:def 12</a></i>
<br/>.= 
the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s1</font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">s1</font></span>)</span></span>)</span>
<b>by </b><i>, <a class="txt" href="graphsp.html#E1:19"><i><font color="Green">E34</font></i></a>, </i>
;<br/><b>set </b><font color="Maroon">Vs</font> =  <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s</font>;<br/><a NAME="E21:19_1"/><i><font color="Green">E100</font></i>: 
<span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v3</font></span><a href="tarski.html#K1">}</a></span> <a href="tarski.html#R1">c=</a> <font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, <a class="ref" href="graph_5.html#D4">GRAPH_5:def 4</a></i>;<br/><div><i><font color="Green">E101</font></i>: <a class="txt" onclick="hs2(this)" href="javascript:()" title="19_1_3"><b>now </b></a><div class="add"><b>assume </b><a NAME="E1:19_1_3"/><i><font color="Green">E102</font></i>: 
<font color="Maroon">vx</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">v2</font>
 ;<br/><a NAME="E2:19_1_3"/><i><font color="Green">E103</font></i>: 
<font color="Maroon">vx</font> <a href="hidden.html#R2">in</a>  <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s</font>
 <b>by </b><i>, , </i>;<br/><a NAME="E3:19_1_3"/>
<font color="Maroon">vx</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font></span>)</span></span>)</span>
 <b>by </b><i>, , <a class="txt" href="graphsp.html#E1:19"><i><font color="Green">E34</font></i></a>, <a class="ref" href="graphsp.html#T2" target="_self">Th2</a>, </i>;<br/><a NAME="E4:19_1_3"/><b>then </b>
not <font color="Maroon">vx</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v3</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><a NAME="E5:19_1_3"/><b>then </b>
<font color="Maroon">vx</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v3</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, <a class="ref" href="xboole_0.html#D4">XBOOLE_0:def 4</a></i>;<br/><a NAME="E6:19_1_3"/><b>then </b><i><font color="Green">E104</font></i>: 
( <font color="Maroon">vx</font> <a href="hidden.html#R2">in</a> <font color="Maroon">V</font> or <font color="Maroon">vx</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i><a class="ref" href="graphsp.html#T3" target="_self">Th3</a>, <a class="ref" href="xboole_0.html#D2">XBOOLE_0:def 2</a></i>;<br/><a NAME="E7:19_1_3"/><i><font color="Green">E105</font></i>: 
<font color="Maroon">s2</font> <a href="funct_1.html#K1">.</a> 1 <a href="graph_4.html#R1">orientedly_joins</a> <font color="Maroon">vx</font>,<font color="Maroon">v3</font>
 <b>by </b><i>, , <a class="ref" href="graph_4.html#D1">GRAPH_4:def 1</a></i>;<br/><a NAME="E8:19_1_3"/>
<font color="Maroon">s2</font> <a href="funct_1.html#K1">.</a> 1 <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font>
 <b>by </b><i>, </i>;<br/><b>hence </b><a NAME="E9:19_1_3"/>
contradiction
 <b>by </b><i>, , , , <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/></div><b>end;</b></div><a NAME="E23:19_1"/>
the <a href="graph_1.html#U3">Source</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s1</font> <a href="funct_1.html#K1">.</a> 1</span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">v1</font>
 <b>by </b><i>, , <a class="txt" href="graphsp.html#E1:19"><i><font color="Green">E34</font></i></a>, </i>;<br/><a NAME="E24:19_1"/><b>then </b><i><font color="Green">E106</font></i>: 
<font color="Maroon">s1</font> <a href="graph_5.html#R1">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v2</font>
 <b>by </b><i>, <a class="ref" href="graphsp.html#T1" target="_self">Th1</a>, <a class="ref" href="graphsp.html#T2" target="_self">Th2</a>, , <a class="ref" href="graph_5.html#D3">GRAPH_5:def 3</a></i>;<br/><a NAME="E25:19_1"/>
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">s2</font> <a href="hidden.html#R1">=</a> 1
 <b>by </b><i/>;<br/><a NAME="E26:19_1"/><b>then </b>
not the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <font color="Maroon">s</font></span>)</span></span>)</span> <a href="hidden.html#R2">in</a>  <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font>
 <b>by </b><i>, , , <a class="txt" href="graphsp.html#E1:19"><i><font color="Green">E34</font></i></a>, <a class="ref" href="graph_5.html#T21">GRAPH_5:21</a></i>;<br/><a NAME="E27:19_1"/><b>then </b><i><font color="Green">E109</font></i>: 
<span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v3</font></span><a href="tarski.html#K1">}</a></span> <a href="hidden.html#R1">=</a>  <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font>
 <b>by </b><i>, <a class="ref" href="zfmisc_1.html#T65">ZFMISC_1:65</a></i>;<br/><a NAME="E28:19_1"/>
 <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font> <a href="tarski.html#R1">c=</a>  <a href="graph_5.html#K2">vertices</a> <span class="p1">(<span class="default"><font color="Maroon">s1</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s2</font></span>)</span>
 <b>by </b><i><a class="ref" href="graph_5.html#T30">GRAPH_5:30</a></i>;<br/><a NAME="E29:19_1"/><b>then </b>
 <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v3</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, , <a class="ref" href="xboole_1.html#T33">XBOOLE_1:33</a></i>;<br/><a NAME="E30:19_1"/><b>then </b>
 <a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="graphsp.html#T3" target="_self">Th3</a>, <a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/><a NAME="E31:19_1"/><b>then </b>
<span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="subset_1.html#K6">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="xboole_1.html#T33">XBOOLE_1:33</a></i>;<br/><a NAME="E32:19_1"/><b>then </b><i><font color="Green">E110</font></i>: 
<span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span> <a href="tarski.html#R1">c=</a> <font color="Maroon">V</font> <a href="subset_1.html#K6">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="xboole_1.html#T40">XBOOLE_1:40</a></i>;<br/><a NAME="E33:19_1"/>
<span class="p1">(<span class="default"><a href="graph_5.html#K2">vertices</a> <font color="Maroon">s1</font></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span> <a href="tarski.html#R1">c=</a> <font color="Maroon">V</font>
 <b>by </b><i>, <a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/><a NAME="E34:19_1"/><b>then </b>
<font color="Maroon">s1</font> <a href="graph_5.html#R2">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v2</font>,<font color="Maroon">V</font>
 <b>by </b><i>, <a class="ref" href="graph_5.html#D4">GRAPH_5:def 4</a></i>;<br/><a NAME="E35:19_1"/><b>then </b><i><font color="Green">E111</font></i>: 
 <a href="graph_5.html#K10">cost</a> <font color="Maroon">P</font>,<font color="Maroon">W</font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="graph_5.html#K10">cost</a> <font color="Maroon">s1</font>,<font color="Maroon">W</font>
 <b>by </b><i>, <a class="ref" href="graph_5.html#D18">GRAPH_5:def 18</a></i>;<br/><a NAME="E36:19_1"/>
<font color="Maroon">s2</font> <a href="finseq_4.html#K4">/.</a> 1 <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font>
 <b>by </b><i/>;<br/><a NAME="E37:19_1"/><b>then </b><i><font color="Green">E112</font></i>: 
<font color="Maroon">s2</font> <a href="funct_1.html#K1">.</a> 1 <a href="hidden.html#R2">in</a> the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font>
 <b>by </b><i>, <a class="ref" href="finseq_4.html#T24">FINSEQ_4:24</a></i>;<br/><a NAME="E38:19_1"/>
( the <a href="graph_1.html#U3">Source</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">e</font> <a href="hidden.html#R1">=</a> <font color="Maroon">v2</font> &amp; the <a href="graph_1.html#U4">Target</a> of <font color="Maroon">G</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">e</font> <a href="hidden.html#R1">=</a> <font color="Maroon">v3</font> )
 <b>by </b><i>, <a class="ref" href="graph_4.html#D1">GRAPH_4:def 1</a></i>;<br/><a NAME="E39:19_1"/><b>then </b>
<font color="Maroon">e</font> <a href="hidden.html#R1">=</a> <font color="Maroon">s2</font> <a href="funct_1.html#K1">.</a> 1
 <b>by </b><i>, , , , , <a class="ref" href="graph_1.html#D4">GRAPH_1:def 4</a></i>;<br/><a NAME="E40:19_1"/><b>then </b><i><font color="Green">E113</font></i>: 
<font color="Maroon">s2</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><font color="Maroon">e</font></span><a href="finseq_1.html#K9">*&gt;</a></span>
 <b>by </b><i>, <a class="ref" href="finseq_1.html#T57">FINSEQ_1:57</a></i>;<br/><a NAME="E41:19_1"/><i><font color="Green">E114</font></i>: 
 <a href="graph_5.html#K10">cost</a> <font color="Maroon">s</font>,<font color="Maroon">W</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="graph_5.html#K10">cost</a> <font color="Maroon">s1</font>,<font color="Maroon">W</font></span>)</span> <a href="real_1.html#K3">+</a> <span class="p1">(<span class="default"><a href="graph_5.html#K10">cost</a> <font color="Maroon">s2</font>,<font color="Maroon">W</font></span>)</span>
 <b>by </b><i>, , <a class="ref" href="graph_5.html#T58">GRAPH_5:58</a></i>;<br/><a NAME="E42:19_1"/>
 <a href="graph_5.html#K10">cost</a> <font color="Maroon">Q</font>,<font color="Maroon">W</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="graph_5.html#K10">cost</a> <font color="Maroon">P</font>,<font color="Maroon">W</font></span>)</span> <a href="real_1.html#K3">+</a> <span class="p1">(<span class="default"><a href="graph_5.html#K10">cost</a> <font color="Maroon">s2</font>,<font color="Maroon">W</font></span>)</span>
 <b>by </b><i>, , , <a class="ref" href="graph_5.html#T58">GRAPH_5:58</a></i>;<br/><a NAME="E43:19_1"/><b>then </b><i><font color="Green">E116</font></i>: 
 <a href="graph_5.html#K10">cost</a> <font color="Maroon">Q</font>,<font color="Maroon">W</font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="graph_5.html#K10">cost</a> <font color="Maroon">s</font>,<font color="Maroon">W</font>
 <b>by </b><i>, , <a class="ref" href="xreal_1.html#T9">XREAL_1:9</a></i>;<br/><a NAME="E44:19_1"/>
 <a href="graph_5.html#K10">cost</a> <font color="Maroon">s</font>,<font color="Maroon">W</font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="graph_5.html#K10">cost</a> <font color="Maroon">S</font>,<font color="Maroon">W</font>
 <b>by </b><i>, , <a class="ref" href="graph_5.html#D18">GRAPH_5:def 18</a></i>;<br/><b>hence </b><a NAME="E45:19_1"/>
 <a href="graph_5.html#K10">cost</a> <font color="Maroon">Q</font>,<font color="Maroon">W</font> <a href="xxreal_0.html#R1">&lt;=</a>  <a href="graph_5.html#K10">cost</a> <font color="Maroon">S</font>,<font color="Maroon">W</font>
 <b>by </b><i>, <a class="ref" href="xxreal_0.html#T2">XXREAL_0:2</a></i>;<br/></div><b>end;</b></div>
<a NAME="E5:19"/><i><font color="Green">E117</font></i>: 
<font color="Maroon">P</font> <a href="graph_5.html#R2">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v2</font>,<font color="Maroon">V</font>
 
<b>by </b><i>, <a class="ref" href="graph_5.html#D18">GRAPH_5:def 18</a></i>;<br/>
<a NAME="E6:19"/><b>then </b>
<font color="Maroon">P</font> <a href="graph_5.html#R1">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v2</font>
 
<b>by </b><i><a class="ref" href="graph_5.html#D4">GRAPH_5:def 4</a></i>;<br/>
<a NAME="E7:19"/><b>then </b>
<font color="Maroon">P</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="graph_5.html#D3">GRAPH_5:def 3</a></i>;<br/>
<a NAME="E8:19"/><b>then </b><i><font color="Green">E118</font></i>: 
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">P</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1
 
<b>by </b><i><a class="ref" href="graph_5.html#T8">GRAPH_5:8</a></i>;<br/>
<b>reconsider </b><font color="Maroon">pe</font> = <span class="p1"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><font color="Maroon">e</font></span><a href="finseq_1.html#K9">*&gt;</a></span> as    <a href="finseq_1.html#M2">FinSequence</a> of the <a href="graph_1.html#U2">Edges</a> of <font color="Maroon">G</font> <b>by </b><i>, <a class="ref" href="finseq_1.html#T95">FINSEQ_1:95</a></i>;<br/>
<a NAME="E10:19"/>
(  <a href="finseq_1.html#K3">len</a> <font color="Maroon">pe</font> <a href="hidden.html#R1">=</a> 1 &amp; <font color="Maroon">pe</font> <a href="funct_1.html#K1">.</a> 1 <a href="hidden.html#R1">=</a> <font color="Maroon">e</font> )
 
<b>by </b><i><a class="ref" href="finseq_1.html#T57">FINSEQ_1:57</a></i>;<br/>
<a NAME="E11:19"/><b>then </b>
<font color="Maroon">Q</font> <a href="graph_5.html#R2">is_orientedpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>,<font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i>, , , <a class="ref" href="graph_5.html#T38">GRAPH_5:38</a></i>;<br/>
<b>hence </b><a NAME="E12:19"/>
<font color="Maroon">Q</font> <a href="graph_5.html#R8">is_shortestpath_of</a> <font color="Maroon">v1</font>,<font color="Maroon">v3</font>,<font color="Maroon">V</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">v2</font></span><a href="tarski.html#K1">}</a></span>,<font color="Maroon">W</font>
 <b>by </b><i>, <a class="ref" href="graph_5.html#D18">GRAPH_5:def 18</a></i>;<br/>


</div>
