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

<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>assume </b><a NAME="E1:87"/><i><font color="Green">E13</font></i>: 
<font color="Maroon">X</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">Y</font>
 ;<br/>

<b>thus </b><span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font> = 
<span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><font color="Maroon">Y</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T17" target="_self">Th17</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <a href="xboole_0.html#K1">{}</a> 
<b>by </b><i><a class="ref" href="xboole_1.html#T4" target="_self">Th4</a></i>
<br/>.= 
<font color="Maroon">X</font>
<b>by </b><i><a class="ref" href="xboole_1.html#T49" target="_self">Th49</a>, <a class="ref" href="xboole_1.html#T41" target="_self">Th41</a></i>
;<br/>


</div>
