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

<b>set </b><font color="Maroon">S'</font> =  <a href="substut1.html#K20" target="_self">Sub_not</a> <font color="Maroon">S</font>;<br/>
<b>assume </b><a NAME="E1:93"/><i><font color="Green">E40</font></i>: 
 <a href="substut1.html#K37" target="_self">CQC_Sub</a> <font color="Maroon">S</font> is    <a href="subset_1.html#M2">Element</a> of  <a href="cqc_lang.html#K7">CQC-WFF</a> 
 ;<br/>

<a NAME="E2:93"/>
 <a href="substut1.html#K37" target="_self">CQC_Sub</a> <span class="p1">(<span class="default"><a href="substut1.html#K20" target="_self">Sub_not</a> <font color="Maroon">S</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="qc_lang1.html#K12">'not'</a> <span class="p1">(<span class="default"><a href="substut1.html#K37" target="_self">CQC_Sub</a> <font color="Maroon">S</font></span>)</span>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:93"/>
 <a href="substut1.html#K37" target="_self">CQC_Sub</a> <span class="p1">(<span class="default"><a href="substut1.html#K20" target="_self">Sub_not</a> <font color="Maroon">S</font></span>)</span> is    <a href="subset_1.html#M2">Element</a> of  <a href="cqc_lang.html#K7">CQC-WFF</a> 
 <b>by </b><i>, <a class="ref" href="cqc_lang.html#T18">CQC_LANG:18</a></i>;<br/>


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