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<b>let </b><font color="Maroon">phi</font> be   <a href="ordinal2.html#NM1">Ordinal-Sequence</a>;<br/><b>let </b><font color="Maroon">psi</font> be   <a href="ordinal2.html#NM1">Ordinal-Sequence</a>;<br/>



<a NAME="E1:17"/>
(  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><font color="Maroon">phi</font> <a href="ordinal4.html#K1">^</a> <font color="Maroon">psi</font></span>)</span> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1">dom</a> <font color="Maroon">phi</font></span>)</span> <a href="ordinal2.html#K10">+^</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1">dom</a> <font color="Maroon">psi</font></span>)</span> &amp; ( for <font color="Olive">A</font> being  <a href="ordinal1.html#NM2">Ordinal</a>  st <font color="Olive">A</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <font color="Maroon">phi</font> holds <br/><span class="p1">(<span class="default"><font color="Maroon">phi</font> <a href="ordinal4.html#K1">^</a> <font color="Maroon">psi</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Olive">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">phi</font> <a href="funct_1.html#K1">.</a> <font color="Olive">A</font> ) )
 
<b>by </b><i><a class="ref" href="ordinal4.html#D1">ORDINAL4:def 1</a></i>;<br/>
<a NAME="E2:17"/><b>then </b>
 <a href="relat_1.html#K1">dom</a> <font color="Maroon">phi</font> <a href="ordinal1.html#R1">c=</a>  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><font color="Maroon">phi</font> <a href="ordinal4.html#K1">^</a> <font color="Maroon">psi</font></span>)</span>
 
<b>by </b><i><a class="ref" href="ordinal3.html#T27">ORDINAL3:27</a></i>;<br/>
<a NAME="E3:17"/><b>then </b><i><font color="Green">E23</font></i>: 
 <a href="relat_1.html#K1">dom</a> <font color="Maroon">phi</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1">dom</a> <span class="p2">(<span class="default"><font color="Maroon">phi</font> <a href="ordinal4.html#K1">^</a> <font color="Maroon">psi</font></span>)</span></span>)</span> <a href="xboole_0.html#K3">/\</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1">dom</a> <font color="Maroon">phi</font></span>)</span>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T28">XBOOLE_1:28</a></i>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="17_1"><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="E1:17_1"/><i><font color="Green">E24</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">phi</font>
 ;<br/><a NAME="E2:17_1"/><b>then </b>
<font color="Maroon">x</font> is   <a href="ordinal1.html#NM2">Ordinal</a>
 <b>by </b><i><a class="ref" href="ordinal1.html#T23">ORDINAL1:23</a></i>;<br/><b>hence </b><a NAME="E3:17_1"/>
<font color="Maroon">phi</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">phi</font> <a href="ordinal4.html#K1">^</a> <font color="Maroon">psi</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font>
 <b>by </b><i>, <a class="ref" href="ordinal4.html#D1">ORDINAL4:def 1</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E5:17"/>
<span class="p1">(<span class="default"><font color="Maroon">phi</font> <a href="ordinal4.html#K1">^</a> <font color="Maroon">psi</font></span>)</span> <a href="ordinal1.html#K2">|</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1">dom</a> <font color="Maroon">phi</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">phi</font>
 <b>by </b><i>, <a class="ref" href="funct_1.html#T68">FUNCT_1:68</a></i>;<br/>


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