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<b>let </b><font color="Maroon" title="c1">s</font> be   <a href="qc_lang1.html#NM8" title="QC_LANG1:NM.8">QC-formula</a>;<br/>

<a NAME="E1:69"/>
(  <a href="cqc_the1.html#NR5" title="CQC_THE1:NR.5">|-</a> <font color="Maroon" title="c1">s</font> iff  <a href="subset_1.html#K1" title="SUBSET_1:func.1">{}</a> <a href="cqc_lang.html#K4" title="CQC_LANG:func.4">CQC-WFF</a>  <a href="cqc_the1.html#R3" title="CQC_THE1:pred.3">|-</a> <font color="Maroon" title="c1">s</font> )
 
<b>by </b><i><a class="ref" href="cqc_the1.html#D10" target="_self" title="CQC_THE1:def.10">Def10</a></i>;<br/>
<b>hence </b><a NAME="E2:69"/>
(  <a href="cqc_the1.html#NR5" title="CQC_THE1:NR.5">|-</a> <font color="Maroon" title="c1">s</font> iff <font color="Maroon" title="c1">s</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="cqc_the1.html#K4" title="CQC_THE1:func.4">TAUT</a>  )
 <b>by </b><i><a class="ref" href="cqc_the1.html#D9" target="_self" title="CQC_THE1:def.9">Def9</a></i>;<br/>


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