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<b>let </b><font color="Maroon" title="c1">X</font> be  non <a href="struct_0.html#V3" title="STRUCT_0:attr.3">empty</a> non <a href="tdlat_3.html#V1" title="TDLAT_3:attr.1">discrete</a> <a href="pre_topc.html#NM1" title="PRE_TOPC:NM.1">TopSpace</a>;<br/><b>let </b><font color="Maroon" title="c2">A0</font> be  non <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a> <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">X</font>;<br/>



<b>assume </b><a NAME="E1:66"/>
<font color="Maroon" title="c2">A0</font> is <a href="tops_1.html#V2" title="TOPS_1:attr.2">boundary</a>
 ;<br/>

<a NAME="E2:66"/><b>then </b>
 ex <font color="Olive" title="b1">X0</font> being <a href="pre_topc.html#V1" title="PRE_TOPC:attr.1">strict</a>  <a href="pre_topc.html#M1" title="PRE_TOPC:mode.1">SubSpace</a> of <font color="Maroon" title="c1">X</font> st <br/>( <font color="Olive" title="b1">X0</font> is <a href="tex_3.html#V3" title="TEX_3:attr.3">boundary</a> &amp; <font color="Maroon" title="c2">A0</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> the <a href="struct_0.html#U1" title="STRUCT_0:sel.1">carrier</a> of <font color="Olive" title="b1">X0</font> )
 
<b>by </b><i><a class="ref" href="tex_3.html#T30" target="_self" title="TEX_3:th.30">Th30</a></i>;<br/>
<b>hence </b><a NAME="E3:66"/>
 ex <font color="Olive" title="b1">X0</font> being <a href="pre_topc.html#V1" title="PRE_TOPC:attr.1">strict</a> <a href="tex_3.html#V3" title="TEX_3:attr.3">boundary</a>  <a href="pre_topc.html#M1" title="PRE_TOPC:mode.1">SubSpace</a> of <font color="Maroon" title="c1">X</font> st <font color="Maroon" title="c2">A0</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> the <a href="struct_0.html#U1" title="STRUCT_0:sel.1">carrier</a> of <font color="Olive" title="b1">X0</font>
 ;<br/>


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