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

<b>assume </b><a NAME="E1:60"/>
 <a href="relat_1.html#K1">dom</a> <font color="Maroon">f</font> is   <a href="relat_1.html#NM1">Relation</a>
 ;<br/>

<b>then reconsider </b><font color="Maroon">R</font> =  <a href="relat_1.html#K1">dom</a> <font color="Maroon">f</font> as   <a href="relat_1.html#NM1">Relation</a> ;<br/>
<a NAME="E3:60"/>
<font color="Maroon">R</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><a href="relat_1.html#K1">dom</a> <font color="Maroon">R</font></span>)</span>,<span class="p2">(<span class="default"><a href="relat_1.html#K2">rng</a> <font color="Maroon">R</font></span>)</span></span><a href="zfmisc_1.html#K2">:]</a></span>
 
<b>by </b><i><a class="ref" href="relat_1.html#T21">RELAT_1:21</a></i>;<br/>
<a NAME="E4:60"/><b>then </b><i><font color="Green">E25</font></i>: 
(  <a href="funct_4.html#K2">~</a> <span class="p1">(<span class="default"><a href="funct_4.html#K2">~</a> <font color="Maroon">f</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">f</font> &amp;  <a href="funct_4.html#K2">~</a> <span class="p1">(<span class="default"><a href="funct_4.html#K2">~</a> <font color="Maroon">g</font></span>)</span> <a href="tarski.html#R1">c=</a> <font color="Maroon">g</font> )
 
<b>by </b><i><a class="ref" href="funct_4.html#T52">FUNCT_4:52</a>, <a class="ref" href="funct_4.html#T53">FUNCT_4:53</a></i>;<br/>
<b>assume </b><a NAME="E5:60"/>
 <a href="funct_4.html#K2">~</a> <font color="Maroon">f</font> <a href="tarski.html#R1">c=</a>  <a href="funct_4.html#K2">~</a> <font color="Maroon">g</font>
 ;<br/>

<a NAME="E6:60"/><b>then </b>
<font color="Maroon">f</font> <a href="tarski.html#R1">c=</a>  <a href="funct_4.html#K2">~</a> <span class="p1">(<span class="default"><a href="funct_4.html#K2">~</a> <font color="Maroon">g</font></span>)</span>
 
<b>by </b><i>, </i>;<br/>
<b>hence </b><a NAME="E7:60"/>
<font color="Maroon">f</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">g</font>
 <b>by </b><i>, <a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/>


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