<?xml version="1.0"?>
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<b>let </b><font color="Maroon">T</font> be   <a href="pre_topc.html#NM1">TopSpace</a>;<br/><b>let </b><font color="Maroon">F</font> be   <a href="struct_0.html#NM3">Subset-Family</a> of <font color="Maroon">T</font>;<br/>



<a NAME="E1:30"/>
 <a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font> is <a href="tops_2.html#V1">open</a>
 
<b>by </b><i/>;<br/>
<a NAME="E2:30"/><b>then </b>
(  <a href="setfam_1.html#K5">union</a> <span class="p1">(<span class="default"><a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font></span>)</span> is <a href="pre_topc.html#V3">open</a> &amp;  <a href="setfam_1.html#K5">union</a> <span class="p1">(<span class="default"><a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font></span>)</span> <a href="tarski.html#R1">c=</a>  <a href="setfam_1.html#K5">union</a> <font color="Maroon">F</font> )
 
<b>by </b><i>, <a class="ref" href="tops_2.html#T26">TOPS_2:26</a></i>;<br/>
<a NAME="E3:30"/><b>then </b>
(  <a href="tops_1.html#K1">Int</a> <span class="p1">(<span class="default"><a href="setfam_1.html#K5">union</a> <span class="p2">(<span class="default"><a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a>  <a href="setfam_1.html#K5">union</a> <span class="p1">(<span class="default"><a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font></span>)</span> &amp;  <a href="tops_1.html#K1">Int</a> <span class="p1">(<span class="default"><a href="setfam_1.html#K5">union</a> <span class="p2">(<span class="default"><a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font></span>)</span></span>)</span> <a href="tarski.html#R1">c=</a>  <a href="tops_1.html#K1">Int</a> <span class="p1">(<span class="default"><a href="setfam_1.html#K5">union</a> <font color="Maroon">F</font></span>)</span> )
 
<b>by </b><i><a class="ref" href="tops_1.html#T48">TOPS_1:48</a>, <a class="ref" href="tops_1.html#T55">TOPS_1:55</a></i>;<br/>
<b>hence </b><a NAME="E4:30"/>
 <a href="setfam_1.html#K5">union</a> <span class="p1">(<span class="default"><a href="tdlat_2.html#K1" target="_self">Int</a> <font color="Maroon">F</font></span>)</span> <a href="tarski.html#R1">c=</a>  <a href="tops_1.html#K1">Int</a> <span class="p1">(<span class="default"><a href="setfam_1.html#K5">union</a> <font color="Maroon">F</font></span>)</span>
 ;<br/>


</div>
