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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>let </b><font color="Maroon">f</font> be   <a href="funct_1.html#NM1">Function</a>;<br/>





<b>assume </b><a NAME="E1:77"/><i><font color="Green">E26</font></i>: 
 <a href="relset_1.html#K4">dom</a> <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X</font>,<font color="Maroon">Y</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">X</font>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="partfun1.html#D4" target="_self">PARTFUN1:def 4</a><br/>

<b>let </b><font color="Maroon">y</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E2:77"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">f</font> <a href="relat_1.html#K9">.:</a> <font color="Maroon">X</font>
 ;<br/>

<b>then consider </b><font color="Maroon">x</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E4:77"/><i><font color="Green">E31</font></i>: 
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <font color="Maroon">f</font> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X</font> &amp; <font color="Maroon">y</font> <a href="hidden.html#R1">=</a> <font color="Maroon">f</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> )
 <b>by </b><i><a class="ref" href="funct_1.html#D12">FUNCT_1:def 12</a></i>;<br/>
<a NAME="E5:77"/>
( <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X</font>,<font color="Maroon">Y</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">y</font> &amp; <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X</font>,<font color="Maroon">Y</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K2">rng</a> <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X</font>,<font color="Maroon">Y</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> &amp;  <a href="relat_1.html#K2">rng</a> <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X</font>,<font color="Maroon">Y</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="tarski.html#R1">c=</a> <font color="Maroon">Y</font> )
 
<b>by </b><i>, , , , <a class="ref" href="funct_1.html#D5">FUNCT_1:def 5</a></i>;<br/>
<b>hence </b><a NAME="E6:77"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Y</font>
 ;<br/>


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