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<b>let </b><font color="Maroon" title="c1">p</font>, <font color="Maroon" title="c2">q</font> be    <a href="subset_1.html#M2" title="SUBSET_1:mode.2">Element</a> of  <a href="cqc_lang.html#K7" title="CQC_LANG:func.7">CQC-WFF</a> ;<br/><b>let </b><font color="Maroon" title="c3">X</font> be   <a href="subset_1.html#NM2" title="SUBSET_1:NM.2">Subset</a> of <a href="cqc_lang.html#K7" title="CQC_LANG:func.7">CQC-WFF</a> ;<br/>





<b>assume </b><b>that </b><br/><a NAME="E1:51"/><i><font color="Green" title="E42">A1</font></i>: 
<font color="Maroon" title="c1">p</font> is <a href="qc_lang1.html#V6" title="QC_LANG1:attr.6">closed</a>
 <b>and </b><br/><a NAME="E2:51"/><i><font color="Green" title="E43">A2</font></i>: 
<font color="Maroon" title="c3">X</font> <a href="subset_1.html#K4" title="SUBSET_1:func.4">\/</a> <span class="p1"><a href="domain_1.html#K6" title="DOMAIN_1:func.6">{</a><span class="default"><font color="Maroon" title="c1">p</font></span><a href="domain_1.html#K6" title="DOMAIN_1:func.6">}</a></span> <a href="cqc_the1.html#R3" title="CQC_THE1:pred.3">|-</a> <font color="Maroon" title="c2">q</font>
 ;<br/>

<a NAME="E3:51"/>
<font color="Maroon" title="c3">X</font> <a href="cqc_the1.html#R3" title="CQC_THE1:pred.3">|-</a> <font color="Maroon" title="c1">p</font> <a href="cqc_lang.html#K12" title="CQC_LANG:func.12">=&gt;</a> <font color="Maroon" title="c2">q</font>
 
<b>by </b><i><a class="txt" href="cqc_the3.html#E1:51"><i><font color="Green" title="E42">A1</font></i></a>, <a class="txt" href="cqc_the3.html#E2:51"><i><font color="Green" title="E43">A2</font></i></a>, <a class="ref" href="cqc_the2.html#T96" title="CQC_THE2:th.96">CQC_THE2:96</a></i>;<br/>
<a NAME="E4:51"/><b>then </b>
<font color="Maroon" title="c3">X</font> <a href="cqc_the1.html#R3" title="CQC_THE1:pred.3">|-</a> <span class="p1">(<span class="default"><a href="cqc_lang.html#K10" title="CQC_LANG:func.10">'not'</a> <font color="Maroon" title="c2">q</font></span>)</span> <a href="cqc_lang.html#K12" title="CQC_LANG:func.12">=&gt;</a> <span class="p1">(<span class="default"><a href="cqc_lang.html#K10" title="CQC_LANG:func.10">'not'</a> <font color="Maroon" title="c1">p</font></span>)</span>
 
<b>by </b><i><a class="ref" href="lukasi_1.html#T86" title="LUKASI_1:th.86">LUKASI_1:86</a></i>;<br/>
<b>hence </b><a NAME="E5:51"/>
<font color="Maroon" title="c3">X</font> <a href="subset_1.html#K4" title="SUBSET_1:func.4">\/</a> <span class="p1"><a href="domain_1.html#K6" title="DOMAIN_1:func.6">{</a><span class="default"><span class="p2">(<span class="default"><a href="cqc_lang.html#K10" title="CQC_LANG:func.10">'not'</a> <font color="Maroon" title="c2">q</font></span>)</span></span><a href="domain_1.html#K6" title="DOMAIN_1:func.6">}</a></span> <a href="cqc_the1.html#R3" title="CQC_THE1:pred.3">|-</a>  <a href="cqc_lang.html#K10" title="CQC_LANG:func.10">'not'</a> <font color="Maroon" title="c1">p</font>
 <b>by </b><i><a class="ref" href="cqc_the3.html#T40" target="_self" title="CQC_THE3:th.40">Th40</a></i>;<br/>


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