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<b>let </b><font color="Maroon">A</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">N</font> be    <a href="pboole.html#M1">ManySortedSet</a> of <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">A</font>,<font color="Maroon">A</font></span><a href="zfmisc_1.html#K3">:]</a></span>, <font color="Maroon">M</font> be    <a href="pboole.html#M1">ManySortedSet</a> of <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">A</font>,<font color="Maroon">A</font></span><a href="zfmisc_1.html#K3">:]</a></span>;<br/>



<b>assume </b><a NAME="E1:15"/><i><font color="Green">E15</font></i>: 
for <font color="Olive">i</font>, <font color="Olive">j</font>, <font color="Olive">k</font> being   <a href="hidden.html#M1">set</a>   st <font color="Olive">i</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> &amp; <font color="Olive">j</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> &amp; <font color="Olive">k</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> holds <br/><font color="Maroon">N</font> <a href="multop_1.html#K1">.</a> <font color="Olive">i</font>,<font color="Olive">j</font>,<font color="Olive">k</font> <a href="hidden.html#R1">=</a> <font color="Maroon">M</font> <a href="multop_1.html#K1">.</a> <font color="Olive">i</font>,<font color="Olive">j</font>,<font color="Olive">k</font>
 ;<br/>

<a NAME="E2:15"/><i><font color="Green">E27</font></i>: 
(  <a href="relat_1.html#K1">dom</a> <font color="Maroon">M</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">A</font>,<font color="Maroon">A</font></span><a href="zfmisc_1.html#K3">:]</a></span> &amp;  <a href="relat_1.html#K1">dom</a> <font color="Maroon">N</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">A</font>,<font color="Maroon">A</font></span><a href="zfmisc_1.html#K3">:]</a></span> )
 
<b>by </b><i><a class="ref" href="pboole.html#D3">PBOOLE:def 3</a></i>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="15_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="E1:15_1"/><i><font color="Green">E28</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">A</font>,<font color="Maroon">A</font></span><a href="zfmisc_1.html#K3">:]</a></span>
 ;<br/><b>then reconsider </b><font color="Maroon">A</font> = <font color="Maroon">A</font> as  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a>  <b>by </b><i><a class="ref" href="mcart_1.html#T35">MCART_1:35</a></i>;<br/><b>consider </b><font color="Maroon">i</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>, <font color="Maroon">j</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>, <font color="Maroon">k</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font><b> such that </b><br/><a NAME="E4:15_1"/><i><font color="Green">E29</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="domain_1.html#K4">[</a><span class="default"><font color="Maroon">i</font>,<font color="Maroon">j</font>,<font color="Maroon">k</font></span><a href="domain_1.html#K4">]</a></span>
 <b>by </b><i>, <a class="ref" href="domain_1.html#T15">DOMAIN_1:15</a></i>;<br/><b>thus </b><font color="Maroon">M</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> = 
<font color="Maroon">M</font> <a href="multop_1.html#K1">.</a> <font color="Maroon">i</font>,<font color="Maroon">j</font>,<font color="Maroon">k</font>
<b>by </b><i>, <a class="ref" href="multop_1.html#D1">MULTOP_1:def 1</a></i>
<br/>.= 
<font color="Maroon">N</font> <a href="multop_1.html#K1">.</a> <font color="Maroon">i</font>,<font color="Maroon">j</font>,<font color="Maroon">k</font>
<b>by </b><i/>
<br/>.= 
<font color="Maroon">N</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font>
<b>by </b><i>, <a class="ref" href="multop_1.html#D1">MULTOP_1:def 1</a></i>
;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E4:15"/>
<font color="Maroon">M</font> <a href="pboole.html#R6">=</a> <font color="Maroon">N</font>
 <b>by </b><i>, <a class="ref" href="funct_1.html#T9">FUNCT_1:9</a></i>;<br/>


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