<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">X</font> be  non <a href="struct_0.html#V3">empty</a> <a href="pre_topc.html#NM1">TopSpace</a>;<br/><b>let </b><font color="Maroon">X1</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="pre_topc.html#M1">SubSpace</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">X2</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="pre_topc.html#M1">SubSpace</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">x</font> be   <a href="pre_topc.html#NM2">Point</a> of <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font></span>)</span>;<br/><b>let </b><font color="Maroon">U1</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">X1</font>;<br/><b>let </b><font color="Maroon">U2</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">X2</font>;<br/>











<b>assume </b><b>that </b><br/><a NAME="E1:21"/><i><font color="Green">E23</font></i>: 
( <font color="Maroon">U1</font> is <a href="pre_topc.html#V3">open</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">U1</font> )
 <b>and </b><br/><a NAME="E2:21"/><i><font color="Green">E29</font></i>: 
( <font color="Maroon">U2</font> is <a href="pre_topc.html#V3">open</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">U2</font> )
 ;<br/>

<a NAME="E3:21"/><i><font color="Green">E35</font></i>: 
<font color="Maroon">X1</font> is    <a href="pre_topc.html#M1">SubSpace</a> of <font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font>
 
<b>by </b><i><a class="ref" href="tsep_1.html#T22">TSEP_1:22</a></i>;<br/>
<b>then consider </b><font color="Maroon">V1</font> being   <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font></span>)</span><b> such that </b><br/><a NAME="E5:21"/><i><font color="Green">E36</font></i>: 
( <font color="Maroon">V1</font> is <a href="pre_topc.html#V3">open</a> &amp; <font color="Maroon">V1</font> <a href="subset_1.html#K9">/\</a> <span class="p1">(<span class="default"><a href="pre_topc.html#K2">[#]</a> <font color="Maroon">X1</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">U1</font> )
 <b>by </b><i>, <a class="ref" href="tops_2.html#T32">TOPS_2:32</a></i>;<br/>
<a NAME="E6:21"/><i><font color="Green">E38</font></i>: 
<font color="Maroon">X2</font> is    <a href="pre_topc.html#M1">SubSpace</a> of <font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font>
 
<b>by </b><i><a class="ref" href="tsep_1.html#T22">TSEP_1:22</a></i>;<br/>
<b>then consider </b><font color="Maroon">V2</font> being   <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font></span>)</span><b> such that </b><br/><a NAME="E8:21"/><i><font color="Green">E39</font></i>: 
( <font color="Maroon">V2</font> is <a href="pre_topc.html#V3">open</a> &amp; <font color="Maroon">V2</font> <a href="subset_1.html#K9">/\</a> <span class="p1">(<span class="default"><a href="pre_topc.html#K2">[#]</a> <font color="Maroon">X2</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">U2</font> )
 <b>by </b><i>, <a class="ref" href="tops_2.html#T32">TOPS_2:32</a></i>;<br/>
<b>take </b><font color="Maroon">V</font> = <font color="Maroon">V1</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">V2</font>;<br/>

<b>reconsider </b><font color="Maroon">C1</font> = the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">X1</font> as   <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font></span>)</span> <b>by </b><i>, <a class="ref" href="tsep_1.html#T1">TSEP_1:1</a></i>;<br/>
<b>reconsider </b><font color="Maroon">C2</font> = the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">X2</font> as   <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font></span>)</span> <b>by </b><i>, <a class="ref" href="tsep_1.html#T1">TSEP_1:1</a></i>;<br/>
<a NAME="E11:21"/>
the <a href="struct_0.html#U1">carrier</a> of <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K1">union</a> <font color="Maroon">X2</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">C1</font> <a href="subset_1.html#K4">\/</a> <font color="Maroon">C2</font>
 
<b>by </b><i><a class="ref" href="tsep_1.html#D2">TSEP_1:def 2</a></i>;<br/>
<b>then </b><i><font color="Green">E42</font></i>: <font color="Maroon">V</font> = 
<font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="subset_1.html#K4">\/</a> <font color="Maroon">C2</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T28">XBOOLE_1:28</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C1</font></span>)</span> <a href="subset_1.html#K4">\/</a> <span class="p1">(<span class="default"><font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C2</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T23">XBOOLE_1:23</a></i>
;<br/>
<a NAME="E13:21"/>
( <font color="Maroon">V</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">V1</font> &amp; <font color="Maroon">V</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">V2</font> )
 
<b>by </b><i><a class="ref" href="xboole_1.html#T17">XBOOLE_1:17</a></i>;<br/>
<a NAME="E14:21"/><b>then </b>
( <font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">V1</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C1</font> &amp; <font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C2</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">V2</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C2</font> )
 
<b>by </b><i><a class="ref" href="xboole_1.html#T26">XBOOLE_1:26</a></i>;<br/>
<a NAME="E15:21"/><b>then </b><i><font color="Green">E43</font></i>: 
( <font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">U1</font> &amp; <font color="Maroon">V</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">C2</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">U2</font> )
 
<b>by </b><i><a class="ref" href="tmap_1.html#T2" target="_self">Th2</a>, </i>;<br/>
<a NAME="E16:21"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">V1</font> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">V2</font> )
 
<b>by </b><i>, , <a class="ref" href="tmap_1.html#T2" target="_self">Th2</a>, , <a class="ref" href="xboole_0.html#D3">XBOOLE_0:def 3</a></i>;<br/>
<b>hence </b><a NAME="E17:21"/>
( <font color="Maroon">V</font> is <a href="pre_topc.html#V3">open</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">V</font> &amp; <font color="Maroon">V</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">U1</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">U2</font> )
 <b>by </b><i><a class="ref" href="tmap_1.html#T2" target="_self">Th2</a>, , <a class="txt" href="tmap_1.html#E1:21"><i><font color="Green">E23</font></i></a>, , <a class="ref" href="tops_1.html#T38">TOPS_1:38</a>, <a class="ref" href="xboole_0.html#D3">XBOOLE_0:def 3</a>, <a class="ref" href="xboole_1.html#T13">XBOOLE_1:13</a></i>;<br/>


</div>
