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<b>let </b><font color="Maroon">T</font> be  non <a href="struct_0.html#V3">empty</a> <a href="pre_topc.html#NM1">TopSpace</a>;<br/>

<b>consider </b><font color="Maroon">x</font> being   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">T</font><b> such that </b><br/><a NAME="E2:7"/><i><font color="Green">E25</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a>  <a href="pre_topc.html#K1">{}</a> <font color="Maroon">T</font>
 ;<br/>
<a NAME="E3:7"/><i><font color="Green">E26</font></i>: 
<font color="Maroon">x</font> is <a href="pre_topc.html#V3">open</a>
 
<b>by </b><i>, <a class="ref" href="tops_1.html#T52">TOPS_1:52</a></i>;<br/>
<a NAME="E4:7"/>
<font color="Maroon">x</font> is <a href="pre_topc.html#V4">closed</a>
 
<b>by </b><i>, <a class="ref" href="tops_1.html#T22">TOPS_1:22</a></i>;<br/>
<b>hence </b><a NAME="E5:7"/>
 <a href="pre_topc.html#K1">{}</a> <font color="Maroon">T</font> is    <a href="subset_1.html#M2">Element</a> of  <a href="lopclset.html#K1" target="_self">OpenClosedSet</a> <font color="Maroon">T</font>
 <b>by </b><i>, , </i>;<br/>


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