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<b>let </b><font color="Maroon">GX</font> be    <a href="pre_topc.html#L1">TopStruct</a> ;<br/><b>let </b><font color="Maroon">S</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">GX</font>;<br/><b>let </b><font color="Maroon">T</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">GX</font>;<br/>





<b>assume </b><a NAME="E1:41"/><i><font color="Green">E21</font></i>: 
( <font color="Maroon">S</font> is <a href="pre_topc.html#V3">open</a> &amp; <font color="Maroon">S</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">T</font> )
 ;<br/>

<a NAME="E2:41"/><b>then </b>
 <a href="tops_1.html#K1" target="_self">Int</a> <font color="Maroon">S</font> <a href="hidden.html#R1">=</a> <font color="Maroon">S</font>
 
<b>by </b><i><a class="ref" href="tops_1.html#T29" target="_self">Th29</a></i>;<br/>
<b>hence </b><a NAME="E3:41"/>
<font color="Maroon">S</font> <a href="tarski.html#R1">c=</a>  <a href="tops_1.html#K1" target="_self">Int</a> <font color="Maroon">T</font>
 <b>by </b><i><a class="ref" href="tops_1.html#T30" target="_self">Th30</a>, </i>;<br/>


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