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<b>let </b><font color="Maroon">c<sub>1</sub></font> be  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <a href="qc_lang1.html#K1">QC-variables</a> ;<br/>

<b>thus </b> <a href="qc_lang3.html#K4" target="_self">Vars</a> <a href="qc_lang2.html#K1">FALSUM</a> ,<font color="Maroon">c<sub>1</sub></font> = 
 <a href="qc_lang3.html#K4" target="_self">Vars</a> <a href="qc_lang1.html#K11">VERUM</a> ,<font color="Maroon">c<sub>1</sub></font>
<b>by </b><i><a class="ref" href="qc_lang3.html#T50" target="_self">Th50</a>, <a class="ref" href="qc_lang2.html#D1">QC_LANG2:def 1</a></i>
<br/>.= 
 <a href="xboole_0.html#K1">{}</a> 
<b>by </b><i><a class="txt" href="qc_lang3.html#E49"><i><font color="Green">Lemma22</font></i></a></i>
;<br/>


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