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<b>let </b><font color="Maroon">p</font> be    <a href="subset_1.html#M2">Element</a> of  <a href="cqc_lang.html#K7">CQC-WFF</a> ;<br/><b>let </b><font color="Maroon">x</font> be    <a href="subset_1.html#M2">Element</a> of  <a href="qc_lang1.html#K2">bound_QC-variables</a> ;<br/>



<a NAME="E1:15"/>
<font color="Maroon">p</font> <a href="qc_lang2.html#R3">is_proper_subformula_of</a>  <a href="cqc_lang.html#K15">All</a> <font color="Maroon">x</font>,<font color="Maroon">p</font>
 
<b>by </b><i><a class="ref" href="qc_lang2.html#T91">QC_LANG2:91</a></i>;<br/>
<b>hence </b><a NAME="E2:15"/>
<font color="Maroon">p</font> <a href="qc_lang2.html#R2">is_subformula_of</a>  <a href="cqc_lang.html#K15">All</a> <font color="Maroon">x</font>,<font color="Maroon">p</font>
 <b>by </b><i><a class="ref" href="qc_lang2.html#D22">QC_LANG2:def 22</a></i>;<br/>


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