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<b>let </b><font color="Maroon">G</font> be   <a href="glib_000.html#NM2">_Graph</a>;<br/><b>let </b><font color="Maroon">W</font> be    <a href="glib_001.html#M3" target="_self">Walk</a> of <font color="Maroon">G</font>;<br/><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">y</font> be    <a href="hidden.html#M1">set</a> ;<br/>







<b>assume </b><a NAME="E1:159"/>
<font color="Maroon">W</font> <a href="glib_001.html#R1" target="_self">is_Walk_from</a> <font color="Maroon">x</font>,<font color="Maroon">y</font>
 ;<br/>

<a NAME="E2:159"/><b>then </b>
( <font color="Maroon">W</font> <a href="glib_001.html#K3" target="_self">.first()</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">x</font> &amp; <font color="Maroon">W</font> <a href="glib_001.html#K4" target="_self">.last()</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">y</font> )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:159"/>
( <font color="Maroon">x</font> is   <a href="glib_000.html#NM10">Vertex</a> of <font color="Maroon">G</font> &amp; <font color="Maroon">y</font> is   <a href="glib_000.html#NM10">Vertex</a> of <font color="Maroon">G</font> )
 ;<br/>


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