<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">I</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">X</font> be    <a href="pboole.html#M1" target="_self">ManySortedSet</a> of <font color="Maroon">I</font>;<br/>



<b>assume </b><a NAME="E1:54"/>
<font color="Maroon">X</font> <a href="pboole.html#R2" target="_self">c=</a>  <a href="pboole.html#K1" target="_self">[0]</a> <font color="Maroon">I</font>
 ;<br/>

<b>hence </b><a NAME="E2:54"/>
( <font color="Maroon">X</font> <a href="pboole.html#R2" target="_self">c=</a>  <a href="pboole.html#K1" target="_self">[0]</a> <font color="Maroon">I</font> &amp;  <a href="pboole.html#K1" target="_self">[0]</a> <font color="Maroon">I</font> <a href="pboole.html#R2" target="_self">c=</a> <font color="Maroon">X</font> )
 <b>by </b><i/>; <i><font color="Red">:: according to </font></i><a class="ref" href="pboole.html#D13" target="_self">PBOOLE:def 13</a><br/>


</div>
