<?xml version="1.0"?>
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<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y</font> be    <a href="hidden.html#M1">set</a> ;<br/>



<b>set </b><font color="Maroon">f</font> = <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span>;<br/>
<b>set </b><font color="Maroon">g</font> = <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span>;<br/>
<a NAME="E1:11"/><i><font color="Green">E34</font></i>: 
 <a href="relat_1.html#K1">dom</a> <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><font color="Maroon">Y</font>,<font color="Maroon">X</font></span><a href="zfmisc_1.html#K2">:]</a></span>
 
<b>by </b><i/>;<br/>
<i><font color="Green">E35</font></i>:  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><span class="p2"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p3">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p3">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="funct_1.html#K2">"</a> </span>)</span> = 
 <a href="relat_1.html#K2">rng</a> <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span>
<b>by </b><i><a class="ref" href="funct_1.html#T54">FUNCT_1:54</a></i>
<br/>.= 
<span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><font color="Maroon">Y</font>,<font color="Maroon">X</font></span><a href="zfmisc_1.html#K2">:]</a></span>
<b>by </b><i/>
;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="11_2"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>assume </b><a NAME="E1:11_2"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><font color="Maroon">Y</font>,<font color="Maroon">X</font></span><a href="zfmisc_1.html#K2">:]</a></span>
 ;<br/><b>then consider </b><font color="Maroon">x1</font> being    <a href="hidden.html#M1">set</a> , <font color="Maroon">x2</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E3:11_2"/><i><font color="Green">E43</font></i>: 
( <font color="Maroon">x1</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Y</font> &amp; <font color="Maroon">x2</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X</font> &amp; <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font></span><a href="tarski.html#K4">]</a></span> )
 <b>by </b><i><a class="ref" href="zfmisc_1.html#D2">ZFMISC_1:def 2</a></i>;<br/><a NAME="E4:11_2"/><i><font color="Green">E46</font></i>: 
<span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="binop_1.html#K1">.</a> <font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">x2</font>,<font color="Maroon">x1</font></span><a href="tarski.html#K4">]</a></span>
 <b>by </b><i>, </i>;<br/><a NAME="E5:11_2"/>
 <a href="relat_1.html#K1">dom</a> <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><font color="Maroon">X</font>,<font color="Maroon">Y</font></span><a href="zfmisc_1.html#K2">:]</a></span>
 <b>by </b><i/>;<br/><a NAME="E6:11_2"/><b>then </b><i><font color="Green">E47</font></i>: 
<span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">x2</font>,<font color="Maroon">x1</font></span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span>
 <b>by </b><i>, <a class="ref" href="zfmisc_1.html#T106">ZFMISC_1:106</a></i>;<br/><a NAME="E7:11_2"/>
<span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="binop_1.html#K1">.</a> <font color="Maroon">x2</font>,<font color="Maroon">x1</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font></span><a href="tarski.html#K4">]</a></span>
 <b>by </b><i>, </i>;<br/><b>hence </b><a NAME="E8:11_2"/>
<span class="p1">(<span class="default"><span class="p2"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p3">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p3">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="funct_1.html#K2">"</a> </span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font>
 <b>by </b><i>, , , <a class="ref" href="funct_1.html#T54">FUNCT_1:54</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E4:11"/>
<span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">X</font>,<font color="Maroon">Y</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span> <a href="funct_1.html#K2">"</a>  <a href="hidden.html#R1">=</a> <span class="p1"><a href="funct_3.html#K13">&lt;:</a><span class="default"><span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span>,<span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">Y</font>,<font color="Maroon">X</font></span>)</span></span><a href="funct_3.html#K13">:&gt;</a></span>
 <b>by </b><i>, , <a class="ref" href="funct_1.html#T9">FUNCT_1:9</a></i>;<br/>


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