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<b>let </b><font color="Maroon" title="c1">p</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="c2">x</font> be   <a href="qc_lang1.html#NM3" title="QC_LANG1:NM.3">bound_QC-variable</a>;<br/>



<a NAME="E1:76"/>
<font color="Maroon" title="c1">p</font> <a href="cqc_lang.html#K14" title="CQC_LANG:func.14">&lt;=&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="txt" href="cqc_the2.html#E17"><i><font color="Green" title="E17">Lm13</font></i></a></i>;<br/>
<b>hence </b><a NAME="E2:76"/>
 <a href="cqc_lang.html#K16" title="CQC_LANG:func.16">Ex</a> <font color="Maroon" title="c2">x</font>,<span class="p1">(<span class="default"><font color="Maroon" title="c1">p</font> <a href="cqc_lang.html#K14" title="CQC_LANG:func.14">&lt;=&gt;</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_the2.html#T19" target="_self" title="CQC_THE2:th.19">Th19</a></i>;<br/>


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