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<b>let </b><font color="Maroon">H</font> be    <a href="subset_1.html#M1">Element</a> of  <a href="qc_lang1.html#K8">QC-WFF</a> ;<br/>

<b>assume </b><a NAME="E1:93"/>
<font color="Maroon">H</font> is <a href="qc_lang1.html#V3">negative</a>
 ;<br/>

<a NAME="E2:93"/><b>then </b>
<font color="Maroon">H</font> <a href="hidden.html#R1">=</a>  <a href="qc_lang1.html#K12">'not'</a> <span class="p1">(<span class="default"><a href="qc_lang1.html#K17">the_argument_of</a> <font color="Maroon">H</font></span>)</span>
 
<b>by </b><i><a class="ref" href="qc_lang1.html#D23">QC_LANG1:def 23</a></i>;<br/>
<b>hence </b><a NAME="E3:93"/>
 <a href="qc_lang2.html#K15" target="_self">Subformulae</a> <font color="Maroon">H</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="qc_lang2.html#K15" target="_self">Subformulae</a> <span class="p2">(<span class="default"><a href="qc_lang1.html#K17">the_argument_of</a> <font color="Maroon">H</font></span>)</span></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">H</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i/>;<br/>


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