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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="subset_1.html#M1">Element</a> of  <a href="qc_lang1.html#K8">QC-WFF</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font>, <font color="Maroon">c<sub>3</sub></font> be    <a href="qc_lang4.html#M1" target="_self">Subformula</a> of <font color="Maroon">c<sub>1</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>4</sub></font> be    <a href="qc_lang4.html#M2" target="_self">Entry_Point_in_Subformula_Tree</a> of <font color="Maroon">c<sub>3</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>5</sub></font> be   <a href="finseq_1.html#NM1">FinSequence</a>;<br/>









<b>assume </b><a NAME="E1:71"/><i><font color="Green">E60</font></i>: 
<font color="Maroon">c<sub>4</sub></font> <a href="finseq_1.html#K7">^</a> <font color="Maroon">c<sub>5</sub></font> is    <a href="qc_lang4.html#M2" target="_self">Entry_Point_in_Subformula_Tree</a> of <font color="Maroon">c<sub>2</sub></font>
 ;<br/>

<a NAME="E2:71"/>
<span class="p1">(<span class="default"><a href="qc_lang4.html#K2" target="_self">tree_of_subformulae</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="trees_2.html#K3">.</a> <font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>3</sub></font>
 
<b>by </b><i><a class="ref" href="qc_lang4.html#D5" target="_self">Def5</a></i>;<br/>
<a NAME="E3:71"/><b>then </b><i><font color="Green">E61</font></i>: 
<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="qc_lang4.html#K3" target="_self">-entry_points_in_subformula_tree_of</a> <font color="Maroon">c<sub>3</sub></font>
 
<b>by </b><i><a class="ref" href="qc_lang4.html#D3" target="_self">Def3</a></i>;<br/>
<b>consider </b><font color="Maroon">c<sub>6</sub></font> being   <a href="finseq_1.html#NM1">FinSequence</a><b> such that </b><br/><a NAME="E5:71"/><i><font color="Green">E62</font></i>: 
<font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="finseq_1.html#K7">^</a> <font color="Maroon">c<sub>5</sub></font>
 ;<br/>
<a NAME="E6:71"/>
<font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <font color="Olive">b<sub>1</sub></font> where B is    <a href="qc_lang4.html#M2" target="_self">Entry_Point_in_Subformula_Tree</a> of <font color="Maroon">c<sub>2</sub></font> : <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Olive">b<sub>1</sub></font> </span>}</span> 
 
<b>by </b><i><a class="txt" href="qc_lang4.html#E1:71"><i><font color="Green">E60</font></i></a>, <a class="txt" href="qc_lang4.html#E5:71"><i><font color="Green">E62</font></i></a></i>;<br/>
<a NAME="E7:71"/><b>then </b><i><font color="Green">E63</font></i>: 
<font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R2">in</a>  <a href="qc_lang4.html#K4" target="_self">entry_points_in_subformula_tree</a> <font color="Maroon">c<sub>2</sub></font>
 
<b>by </b><i><a class="ref" href="qc_lang4.html#T68" target="_self">Th68</a></i>;<br/>
<b>thus </b><a NAME="E8:71"/>
<font color="Maroon">c<sub>5</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>3</sub></font> <a href="qc_lang4.html#K3" target="_self">-entry_points_in_subformula_tree_of</a> <font color="Maroon">c<sub>2</sub></font>
 <b>by </b><i><a class="txt" href="qc_lang4.html#E3:71"><i><font color="Green">E61</font></i></a>, <a class="txt" href="qc_lang4.html#E5:71"><i><font color="Green">E62</font></i></a>, <a class="txt" href="qc_lang4.html#E7:71"><i><font color="Green">E63</font></i></a>, <a class="ref" href="qc_lang4.html#T58" target="_self">Th58</a></i>;<br/>


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