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<b>let </b><font color="Maroon" title="c1">TS</font> be   <a href="pre_topc.html#NM1" title="PRE_TOPC:NM.1">TopSpace</a>;<br/><b>let </b><font color="Maroon" title="c2">P</font>, <font color="Maroon" title="c3">Q</font> be   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">TS</font>;<br/>





<a NAME="E1:107"/><i><font color="Green" title="E61">A1</font></i>: 
<span class="p1">(<span class="default"><font color="Maroon" title="c2">P</font> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a> </span>)</span> <a href="subset_1.html#K4" title="SUBSET_1:func.4">\/</a> <span class="p1">(<span class="default"><font color="Maroon" title="c3">Q</font> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a> </span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">P</font> <a href="subset_1.html#K9" title="SUBSET_1:func.9">/\</a> <font color="Maroon" title="c3">Q</font></span>)</span> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a> 
 
<b>by </b><i><a class="ref" href="xboole_1.html#T54" title="XBOOLE_1:th.54">XBOOLE_1:54</a></i>;<br/>
<b>assume </b><a NAME="E2:107"/>
( <font color="Maroon" title="c2">P</font> is <a href="tops_1.html#V6" title="TOPS_1:attr.6">open_condensed</a> &amp; <font color="Maroon" title="c3">Q</font> is <a href="tops_1.html#V6" title="TOPS_1:attr.6">open_condensed</a> )
 ;<br/>

<a NAME="E3:107"/><b>then </b>
( <font color="Maroon" title="c2">P</font> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a>  is <a href="tops_1.html#V5" title="TOPS_1:attr.5">closed_condensed</a> &amp; <font color="Maroon" title="c3">Q</font> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a>  is <a href="tops_1.html#V5" title="TOPS_1:attr.5">closed_condensed</a> )
 
<b>by </b><i><a class="ref" href="tops_1.html#T101" target="_self" title="TOPS_1:th.101">Th101</a></i>;<br/>
<a NAME="E4:107"/><b>then </b>
<span class="p1">(<span class="default"><font color="Maroon" title="c2">P</font> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a> </span>)</span> <a href="subset_1.html#K4" title="SUBSET_1:func.4">\/</a> <span class="p1">(<span class="default"><font color="Maroon" title="c3">Q</font> <a href="subset_1.html#K3" title="SUBSET_1:func.3">`</a> </span>)</span> is <a href="tops_1.html#V5" title="TOPS_1:attr.5">closed_condensed</a>
 
<b>by </b><i><a class="ref" href="tops_1.html#T108" target="_self" title="TOPS_1:th.108">Th108</a></i>;<br/>
<b>hence </b><a NAME="E5:107"/>
<font color="Maroon" title="c2">P</font> <a href="subset_1.html#K9" title="SUBSET_1:func.9">/\</a> <font color="Maroon" title="c3">Q</font> is <a href="tops_1.html#V6" title="TOPS_1:attr.6">open_condensed</a>
 <b>by </b><i><a class="txt" href="tops_1.html#E1:107"><i><font color="Green" title="E61">A1</font></i></a>, <a class="ref" href="tops_1.html#T101" target="_self" title="TOPS_1:th.101">Th101</a></i>;<br/>


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