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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">v</font> be   <a href="glib_000.html#NM10">Vertex</a> of <font color="Maroon">G</font>;<br/>



<b>set </b><font color="Maroon">RFD</font> = <font color="Maroon">G</font> <a href="glib_002.html#K2" target="_self">.reachableDFrom</a> <font color="Maroon">v</font>;<br/>
<b>set </b><font color="Maroon">RFV</font> = <font color="Maroon">G</font> <a href="glib_002.html#K1" target="_self">.reachableFrom</a> <font color="Maroon">v</font>;<br/>
<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:70"/><i><font color="Green">E41</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">G</font> <a href="glib_002.html#K2" target="_self">.reachableDFrom</a> <font color="Maroon">v</font>
 ;<br/>

<b>then reconsider </b><font color="Maroon">x'</font> = <font color="Maroon">x</font> as   <a href="glib_000.html#NM10">Vertex</a> of <font color="Maroon">G</font> ;<br/>
<b>consider </b><font color="Maroon">W</font> being  <a href="glib_001.html#V2">directed</a>  <a href="glib_001.html#M3">Walk</a> of <font color="Maroon">G</font><b> such that </b><br/><a NAME="E4:70"/><i><font color="Green">E42</font></i>: 
<font color="Maroon">W</font> <a href="glib_001.html#R1">is_Walk_from</a> <font color="Maroon">v</font>,<font color="Maroon">x'</font>
 <b>by </b><i>, </i>;<br/>
<b>thus </b><a NAME="E5:70"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">G</font> <a href="glib_002.html#K1" target="_self">.reachableFrom</a> <font color="Maroon">v</font>
 <b>by </b><i>, </i>;<br/>


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