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<b>let </b><font color="Maroon">y</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Ch</font> be   <a href="funct_1.html#NM1">Function</a>;<br/><b>let </b><font color="Maroon">F</font> be   <a href="funct_1.html#NM1">Function</a>;<br/>





<b>assume </b><a NAME="E1:39"/><i><font color="Green">E47</font></i>: 
<font color="Maroon">Ch</font> <a href="relat_1.html#K10">"</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y</font></span><a href="tarski.html#K1">}</a></span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<b>reconsider </b><font color="Maroon">E</font> =  <a href="xboole_0.html#K1">{}</a>  as    <a href="hidden.html#M1">set</a>  ;<br/>
<a NAME="E3:39"/>
<font color="Maroon">Ch</font> <a href="relat_1.html#K7">|</a> <font color="Maroon">E</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">Ch</font>
 
<b>by </b><i><a class="ref" href="relat_1.html#T88">RELAT_1:88</a></i>;<br/>
<a NAME="E4:39"/><b>then </b>
<span class="p1">(<span class="default"><font color="Maroon">Ch</font> <a href="relat_1.html#K7">|</a> <font color="Maroon">E</font></span>)</span> <a href="relat_1.html#K10">"</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y</font></span><a href="tarski.html#K1">}</a></span> <a href="tarski.html#R1">c=</a> <font color="Maroon">Ch</font> <a href="relat_1.html#K10">"</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y</font></span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i><a class="ref" href="relat_1.html#T179">RELAT_1:179</a></i>;<br/>
<a NAME="E5:39"/><b>then </b>
( <span class="p1">(<span class="default"><font color="Maroon">Ch</font> <a href="relat_1.html#K7">|</a> <font color="Maroon">E</font></span>)</span> <a href="relat_1.html#K10">"</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y</font></span><a href="tarski.html#K1">}</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">Ch</font> <a href="relat_1.html#K10">"</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y</font></span><a href="tarski.html#K1">}</a></span> &amp; <font color="Maroon">Ch</font> <a href="relat_1.html#K7">|</a> <font color="Maroon">E</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  &amp;  <a href="card_fin.html#K2" target="_self">Intersection</a> <font color="Maroon">F</font>,<a href="xboole_0.html#K1">{}</a> ,<font color="Maroon">y</font> <a href="hidden.html#R1">=</a>  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><a href="relat_1.html#K2">rng</a> <font color="Maroon">F</font></span>)</span> )
 
<b>by </b><i>, <a class="ref" href="xboole_1.html#T3">XBOOLE_1:3</a>, , <a class="ref" href="relat_1.html#T110">RELAT_1:110</a></i>;<br/>
<b>hence </b><a NAME="E6:39"/>
 <a href="card_fin.html#K2" target="_self">Intersection</a> <font color="Maroon">F</font>,<font color="Maroon">Ch</font>,<font color="Maroon">y</font> <a href="hidden.html#R1">=</a>  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><a href="relat_1.html#K2">rng</a> <font color="Maroon">F</font></span>)</span>
 <b>by </b><i/>;<br/>


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