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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>, <font color="Maroon">c<sub>3</sub></font>, <font color="Maroon">c<sub>4</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>5</sub></font> be   <a href="glib_000.html#NM10">Vertex</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>









<b>set </b><font color="Maroon">c<sub>6</sub></font> = <font color="Maroon">c<sub>1</sub></font> <a href="glib_002.html#K2" target="_self">.reachableDFrom</a> <font color="Maroon">c<sub>5</sub></font>;<br/>
<b>assume </b><a NAME="E1:69"/><i><font color="Green">E44</font></i>: 
( <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>1</sub></font> <a href="glib_002.html#K2" target="_self">.reachableDFrom</a> <font color="Maroon">c<sub>5</sub></font> &amp; <font color="Maroon">c<sub>3</sub></font> <a href="glib_000.html#R2">DJoins</a> <font color="Maroon">c<sub>2</sub></font>,<font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>1</sub></font> )
 ;<br/>

<b>then consider </b><font color="Maroon">c<sub>7</sub></font> being  <a href="glib_001.html#V2">directed</a>  <a href="glib_001.html#M3">Walk</a> of <font color="Maroon">c<sub>1</sub></font><b> such that </b><br/><a NAME="E3:69"/><i><font color="Green">E45</font></i>: 
<font color="Maroon">c<sub>7</sub></font> <a href="glib_001.html#R1">is_Walk_from</a> <font color="Maroon">c<sub>5</sub></font>,<font color="Maroon">c<sub>2</sub></font>
 <b>by </b><i><a class="ref" href="glib_002.html#D6" target="_self">Def6</a></i>;<br/>
<a NAME="E4:69"/>
( <font color="Maroon">c<sub>7</sub></font> <a href="glib_001.html#K10">.addEdge</a> <font color="Maroon">c<sub>3</sub></font> is <a href="glib_001.html#V2">directed</a> &amp; <font color="Maroon">c<sub>7</sub></font> <a href="glib_001.html#K10">.addEdge</a> <font color="Maroon">c<sub>3</sub></font> <a href="glib_001.html#R1">is_Walk_from</a> <font color="Maroon">c<sub>5</sub></font>,<font color="Maroon">c<sub>4</sub></font> )
 
<b>by </b><i><a class="txt" href="glib_002.html#E1:69"><i><font color="Green">E44</font></i></a>, <a class="txt" href="glib_002.html#E3:69"><i><font color="Green">E45</font></i></a>, <a class="ref" href="glib_001.html#T124">GLIB_001:124</a></i>;<br/>
<b>hence </b><a NAME="E5:69"/>
<font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>1</sub></font> <a href="glib_002.html#K2" target="_self">.reachableDFrom</a> <font color="Maroon">c<sub>5</sub></font>
 <b>by </b><i><a class="ref" href="glib_002.html#D6" target="_self">Def6</a></i>;<br/>


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