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<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></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="E1:60"/><i><font color="Green">E42</font></i>: 
( <font color="Maroon">c<sub>1</sub></font> <a href="qc_lang2.html#R2" target="_self">is_subformula_of</a> <font color="Maroon">c<sub>2</sub></font> &amp; <font color="Maroon">c<sub>2</sub></font> <a href="qc_lang2.html#R1" target="_self">is_immediate_constituent_of</a> <font color="Maroon">c<sub>1</sub></font> )
 ;<br/>

<a NAME="E2:60"/><b>then </b>
<font color="Maroon">c<sub>2</sub></font> <a href="qc_lang2.html#R3" target="_self">is_proper_subformula_of</a> <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="ref" href="qc_lang2.html#T73" target="_self">Th73</a></i>;<br/>
<b>hence </b><a NAME="E3:60"/>
contradiction
 <b>by </b><i><a class="txt" href="qc_lang2.html#E1:60"><i><font color="Green">E42</font></i></a>, <a class="ref" href="qc_lang2.html#T79" target="_self">Th79</a></i>;<br/>


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