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<b>let </b><font color="Maroon">G</font> be  <a href="topgrp_1.html#V4" target="_self">BinContinuous</a> <a href="topgrp_1.html#NM4">TopGroup</a>;<br/><b>let </b><font color="Maroon">O</font> be  <a href="pre_topc.html#V3">open</a> <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">G</font>;<br/><b>let </b><font color="Maroon">a</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">G</font>;<br/>





<a NAME="E1:95"/>
<font color="Maroon">a</font> <a href="group_2.html#K3">*</a> <font color="Maroon">O</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="topgrp_1.html#K7" target="_self">*</a> </span>)</span> <a href="relset_1.html#K10">.:</a> <font color="Maroon">O</font>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E2:95"/>
<font color="Maroon">a</font> <a href="group_2.html#K3">*</a> <font color="Maroon">O</font> is <a href="pre_topc.html#V3">open</a>
 <b>by </b><i/>;<br/>


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