<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">x</font> be   <a href="qc_lang1.html#NM3">bound_QC-variable</a>;<br/><b>let </b><font color="Maroon">a</font> be   <a href="qc_lang1.html#NM5">free_QC-variable</a>;<br/>



<b>set </b><font color="Maroon">f</font> = <font color="Maroon">a</font> <a href="cqc_lang.html#K3" target="_self">.--&gt;</a> <font color="Maroon">x</font>;<br/>
<a NAME="E1:11"/>
( <font color="Maroon">a</font> <a href="hidden.html#R2">in</a>  <a href="qc_lang1.html#K4">free_QC-variables</a>  &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="qc_lang1.html#K1">QC-variables</a>  &amp;  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="cqc_lang.html#K3" target="_self">.--&gt;</a> <font color="Maroon">x</font></span>)</span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">a</font></span><a href="tarski.html#K1">}</a></span> &amp;  <a href="relat_1.html#K2">rng</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="cqc_lang.html#K3" target="_self">.--&gt;</a> <font color="Maroon">x</font></span>)</span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">x</font></span><a href="tarski.html#K1">}</a></span> )
 
<b>by </b><i/>;<br/>
<a NAME="E2:11"/><b>then </b>
(  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="cqc_lang.html#K3" target="_self">.--&gt;</a> <font color="Maroon">x</font></span>)</span> <a href="tarski.html#R1">c=</a>  <a href="qc_lang1.html#K4">free_QC-variables</a>  &amp;  <a href="relat_1.html#K2">rng</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="cqc_lang.html#K3" target="_self">.--&gt;</a> <font color="Maroon">x</font></span>)</span> <a href="tarski.html#R1">c=</a>  <a href="qc_lang1.html#K1">QC-variables</a>  )
 
<b>by </b><i><a class="ref" href="zfmisc_1.html#T37">ZFMISC_1:37</a></i>;<br/>
<b>hence </b><a NAME="E3:11"/>
<font color="Maroon">a</font> <a href="cqc_lang.html#K3" target="_self">.--&gt;</a> <font color="Maroon">x</font> is   <a href="cqc_lang.html#NM1">Substitution</a>
 <b>by </b><i><a class="ref" href="relset_1.html#T11">RELSET_1:11</a></i>;<br/>


</div>
