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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E6">Th9</font></span>: <a NAME="T9"><span class="comment"><font color="firebrick">:: TOPS_2:9</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">T</font> being    <a href="pre_topc.html#L1" title="PRE_TOPC:struct.1">TopStruct</a> <br/>  for <font color="Olive" title="b2">F</font> being   <a href="struct_0.html#NM3" title="STRUCT_0:NM.3">Subset-Family</a> of <font color="Olive" title="b1">T</font> holds <br/> ( <font color="Olive" title="b2">F</font> is  <a href="tops_2.html#V2" title="TOPS_2:attr.2">closed</a>  iff  <a href="setfam_1.html#K7" title="SETFAM_1:func.7">COMPLEMENT</a> <font color="Olive" title="b2">F</font> is  <a href="tops_2.html#V1" title="TOPS_2:attr.1">open</a>  )</div></div>
