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<b>let </b><font color="Maroon" title="c1">T</font> be  non <a href="struct_0.html#V3" title="STRUCT_0:attr.3">empty</a> <a href="pre_topc.html#NM1" title="PRE_TOPC:NM.1">TopSpace</a>;<br/><b>let </b><font color="Maroon" title="c2">F</font>, <font color="Maroon" title="c3">G</font> be   <a href="struct_0.html#NM3" title="STRUCT_0:NM.3">Subset-Family</a> of <font color="Maroon" title="c1">T</font>;<br/>



<b>assume </b><a NAME="E1:9"/><i><font color="Green" title="E6">A1</font></i>: 
<font color="Maroon" title="c2">F</font> is <a href="nagata_1.html#V1" title="NAGATA_1:attr.1">discrete</a>
 ;<br/>

<a NAME="E2:9"/>
<font color="Maroon" title="c2">F</font> <a href="subset_1.html#K7" title="SUBSET_1:func.7">\</a> <font color="Maroon" title="c3">G</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a> <font color="Maroon" title="c2">F</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T36" title="XBOOLE_1:th.36">XBOOLE_1:36</a></i>;<br/>
<b>hence </b><a NAME="E3:9"/>
<font color="Maroon" title="c2">F</font> <a href="subset_1.html#K7" title="SUBSET_1:func.7">\</a> <font color="Maroon" title="c3">G</font> is <a href="nagata_1.html#V1" title="NAGATA_1:attr.1">discrete</a>
 <b>by </b><i><a class="txt" href="nagata_1.html#E1:9"><i><font color="Green" title="E6">A1</font></i></a>, <a class="ref" href="nagata_1.html#T2" target="_self" title="NAGATA_1:th.2">Th2</a></i>;<br/>


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