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<b>let </b><font color="Maroon">S1</font> be    <a href="subset_1.html#M1">Element</a> of  <a href="substut1.html#K16" target="_self">QC-Sub-WFF</a> ;<br/><b>let </b><font color="Maroon">S2</font> be    <a href="subset_1.html#M1">Element</a> of  <a href="substut1.html#K16" target="_self">QC-Sub-WFF</a> ;<br/>



<b>assume </b><a NAME="E1:63"/><i><font color="Green">E40</font></i>: 
<font color="Maroon">S1</font> <a href="substut1.html#K19" target="_self">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">S2</font> <a href="substut1.html#K19" target="_self">`2</a> 
 ;<br/>

<a NAME="E2:63"/><b>then </b>
 <a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Maroon">S1</font>,<font color="Maroon">S2</font> is <a href="substut1.html#V6" target="_self">Sub_conjunctive</a>
 
<b>by </b><i/>;<br/>
<b>then consider </b><font color="Maroon">S2'</font> being    <a href="subset_1.html#M1">Element</a> of  <a href="substut1.html#K16" target="_self">QC-Sub-WFF</a> <b> such that </b><br/><a NAME="E4:63"/><i><font color="Green">E43</font></i>: 
(  <a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Maroon">S1</font>,<font color="Maroon">S2</font> <a href="hidden.html#R1">=</a>  <a href="substut1.html#K21" target="_self">Sub_&amp;</a> <span class="p1">(<span class="default"><a href="substut1.html#K28" target="_self">Sub_the_left_argument_of</a> <span class="p2">(<span class="default"><a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Maroon">S1</font>,<font color="Maroon">S2</font></span>)</span></span>)</span>,<font color="Maroon">S2'</font> &amp; <span class="p1">(<span class="default"><a href="substut1.html#K28" target="_self">Sub_the_left_argument_of</a> <span class="p2">(<span class="default"><a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Maroon">S1</font>,<font color="Maroon">S2</font></span>)</span></span>)</span> <a href="substut1.html#K19" target="_self">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">S2'</font> <a href="substut1.html#K19" target="_self">`2</a>  )
 <b>by </b><i/>;<br/>
<b>thus </b><a NAME="E5:63"/>
 <a href="substut1.html#K28" target="_self">Sub_the_left_argument_of</a> <span class="p1">(<span class="default"><a href="substut1.html#K21" target="_self">Sub_&amp;</a> <font color="Maroon">S1</font>,<font color="Maroon">S2</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">S1</font>
 <b>by </b><i>, <a class="ref" href="substut1.html#T1" target="_self">Th1</a>, </i>;<br/>


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