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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>assume </b><a NAME="E1:61"/>
 <a href="cqc_lang.html#K10" title="CQC_LANG:func.10">'not'</a> <font color="Maroon" title="c1">p</font> <a href="cqc_the3.html#R7" title="CQC_THE3:pred.7">&lt;==&gt;</a>  <a href="cqc_lang.html#K10" title="CQC_LANG:func.10">'not'</a> <font color="Maroon" title="c2">q</font>
 ;<br/>

<a NAME="E2:61"/><b>then </b>
( <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> <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="c2">q</font></span>)</span> is <a href="cqc_the1.html#V2" title="CQC_THE1:attr.2">valid</a> &amp; <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> is <a href="cqc_the1.html#V2" title="CQC_THE1:attr.2">valid</a> )
 
<b>by </b><i><a class="ref" href="cqc_the3.html#T50" target="_self" title="CQC_THE3:th.50">Th50</a></i>;<br/>
<a NAME="E3:61"/><b>then </b>
( <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> is <a href="cqc_the1.html#V2" title="CQC_THE1:attr.2">valid</a> &amp; <font color="Maroon" title="c2">q</font> <a href="cqc_lang.html#K12" title="CQC_LANG:func.12">=&gt;</a> <font color="Maroon" title="c1">p</font> is <a href="cqc_the1.html#V2" title="CQC_THE1:attr.2">valid</a> )
 
<b>by </b><i><a class="ref" href="lukasi_1.html#T63" title="LUKASI_1:th.63">LUKASI_1:63</a></i>;<br/>
<b>hence </b><a NAME="E4:61"/>
<font color="Maroon" title="c1">p</font> <a href="cqc_the3.html#R7" title="CQC_THE3:pred.7">&lt;==&gt;</a> <font color="Maroon" title="c2">q</font>
 <b>by </b><i><a class="ref" href="cqc_the3.html#T50" target="_self" title="CQC_THE3:th.50">Th50</a></i>;<br/>


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