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

<b>let </b><font color="Maroon">TS</font> be   <a href="pre_topc.html#NM1">TopSpace</a>;<br/><b>let </b><font color="Maroon">K</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">TS</font>;<br/>



<a NAME="E1:63"/><i><font color="Green">E21</font></i>: 
 <a href="tops_1.html#K1" target="_self">Int</a> <span class="p1">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <span class="p2">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i/>;<br/>
 <a href="tops_1.html#K2" target="_self">Fr</a> <span class="p1">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <span class="p2">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span></span>)</span> = 
<span class="p1">(<span class="default"><a href="pre_topc.html#K4">Cl</a> <span class="p2">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <span class="p3">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span></span>)</span></span>)</span> <a href="subset_1.html#K7">\</a> <span class="p1">(<span class="default"><a href="tops_1.html#K1" target="_self">Int</a> <span class="p2">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <span class="p3">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span></span>)</span></span>)</span>
<b>by </b><i/>
<br/>.= 
 <a href="tops_1.html#K2" target="_self">Fr</a> <span class="p1">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span>
<b>by </b><i>, </i>
;<br/>
<b>hence </b><a NAME="E3:63"/>
 <a href="tops_1.html#K2" target="_self">Fr</a> <span class="p1">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <span class="p2">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a>  <a href="tops_1.html#K2" target="_self">Fr</a> <span class="p1">(<span class="default"><a href="tops_1.html#K2" target="_self">Fr</a> <font color="Maroon">K</font></span>)</span>
 ;<br/>


</div>
