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

<b>let </b><font color="Maroon">C1</font> be   <a href="coh_sp.html#NM1">Coherence_Space</a>;<br/><b>let </b><font color="Maroon">C2</font> be   <a href="coh_sp.html#NM1">Coherence_Space</a>;<br/>



<b>set </b><font color="Maroon">C</font> = <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>;<br/>
<b>thus </b><a NAME="E1:155"/>
 <a href="cohsp_1.html#K13" target="_self">'not'</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font></span>)</span> <a href="cohsp_1.html#K16" target="_self">"\/"</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font></span>)</span>
  <i><font color="Red">:: according to </font></i><a class="ref" href="xboole_0.html#D10">XBOOLE_0:def 10</a><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:155_1"/><i><font color="Green">E26</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="cohsp_1.html#K13" target="_self">'not'</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font></span>)</span>
 ;<br/>

<a NAME="E2:155_1"/><b>then </b><i><font color="Green">E27</font></i>: 
( <font color="Maroon">x</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font></span>)</span> &amp; ( for <font color="Olive">a</font> being   <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>  ex <font color="Olive">z</font> being   <a href="hidden.html#M1">set</a>  st <font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <font color="Olive">a</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Olive">z</font></span><a href="tarski.html#K1">}</a></span> ) )
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<a NAME="E3:155_1"/>
 <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font></span>)</span> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="tarski.html#K3">union</a> <font color="Maroon">C1</font></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><a href="tarski.html#K3">union</a> <font color="Maroon">C2</font></span>)</span>
 
<b>by </b><i/>;<br/>
<b>then consider </b><font color="Maroon">x1</font> being    <a href="hidden.html#M1">set</a> , <font color="Maroon">x2</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E5:155_1"/><i><font color="Green">E36</font></i>: 
( <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x1</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">x2</font> &amp; <font color="Maroon">x1</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C1</font> &amp; <font color="Maroon">x2</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C2</font> )
 <b>by </b><i>, <a class="ref" href="cohsp_1.html#T21" target="_self">Th21</a></i>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">a</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C1</font>;<br/><b>reconsider </b><font color="Maroon">b</font> =  <a href="xboole_0.html#K1">{}</a>  as    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C2</font> <b>by </b><i><a class="ref" href="coh_sp.html#T1">COH_SP:1</a></i>;<br/><a NAME="E2:155_1_1"/>
<font color="Maroon">a</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">b</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>
 ;<br/><b>then consider </b><font color="Maroon">z</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E4:155_1_1"/><i><font color="Green">E41</font></i>: 
<font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">b</font></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, <a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/><a NAME="E5:155_1_1"/>
<span class="p1">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, , </i>;<br/><a NAME="E6:155_1_1"/><b>then </b>
( <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> &amp; <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i>, <a class="ref" href="xboole_1.html#T7">XBOOLE_1:7</a></i>;<br/><a NAME="E7:155_1_1"/><b>then </b><i><font color="Green">E42</font></i>: 
<span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_1_1"><b>now </b></a><div class="add"><b>thus </b><a NAME="E1:155_1_1_1"/>
( <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  implies <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i><a class="ref" href="xboole_1.html#T2">XBOOLE_1:2</a></i>;<br/><b>assume </b><a NAME="E2:155_1_1_1"/>
<font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/><b>then reconsider </b><font color="Maroon">A</font> = <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> as  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a>  ;<br/><b>consider </b><font color="Maroon">z1</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>;<br/><b>reconsider </b><font color="Maroon">zz</font> = <font color="Maroon">z1</font> as    <a href="hidden.html#M1">set</a>  ;<br/><b>take </b><font color="Maroon">zz</font> = <font color="Maroon">zz</font>;<br/><b>thus </b><a NAME="E6:155_1_1_1"/>
<font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">zz</font></span><a href="tarski.html#K1">}</a></span>
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_1_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">y</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:155_1_1_1_1"/><i><font color="Green">E43</font></i>: 
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font>
 ;<br/>

<a NAME="E2:155_1_1_1_1"/>
1 <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<a NAME="E3:155_1_1_1_1"/><b>then </b>
( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y</font>,1</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,1</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> )
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T24" target="_self">Th24</a>, <a class="ref" href="zfmisc_1.html#T106">ZFMISC_1:106</a></i>;<br/>
<a NAME="E4:155_1_1_1_1"/><b>then </b>
( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y</font>,1</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,1</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> )
 
<b>by </b><i>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<a NAME="E5:155_1_1_1_1"/><b>then </b>
<font color="Maroon">y</font> <a href="hidden.html#R1">=</a> <font color="Maroon">z1</font>
 
<b>by </b><i><a class="ref" href="zfmisc_1.html#T33">ZFMISC_1:33</a></i>;<br/>
<b>hence </b><a NAME="E6:155_1_1_1_1"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">zz</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>


</div><b>end;</b></div></div><b>end;</b></div><b>hence </b><a NAME="E9:155_1_1"/>
 ex <font color="Olive">z</font> being   <a href="hidden.html#M1">set</a>  st <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Olive">z</font></span><a href="tarski.html#K1">}</a></span>
 ;<br/></div><b>end;</b></div>
<b>then reconsider </b><font color="Maroon">x1</font> = <font color="Maroon">x1</font> as    <a href="subset_1.html#M1">Element</a> of  <a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font> <b>by </b><i>, <a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_2"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">b</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C2</font>;<br/><b>reconsider </b><font color="Maroon">a</font> =  <a href="xboole_0.html#K1">{}</a>  as    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C1</font> <b>by </b><i><a class="ref" href="coh_sp.html#T1">COH_SP:1</a></i>;<br/><a NAME="E2:155_1_2"/>
<font color="Maroon">a</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">b</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>
 ;<br/><b>then consider </b><font color="Maroon">z</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E4:155_1_2"/><i><font color="Green">E44</font></i>: 
<font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">b</font></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, <a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/><a NAME="E5:155_1_2"/>
<span class="p1">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, , </i>;<br/><a NAME="E6:155_1_2"/><b>then </b>
( <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> &amp; <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">1</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i>, <a class="ref" href="xboole_1.html#T7">XBOOLE_1:7</a></i>;<br/><a NAME="E7:155_1_2"/><b>then </b><i><font color="Green">E45</font></i>: 
<span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_2_1"><b>now </b></a><div class="add"><b>thus </b><a NAME="E1:155_1_2_1"/>
( <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  implies <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i><a class="ref" href="xboole_1.html#T2">XBOOLE_1:2</a></i>;<br/><b>assume </b><a NAME="E2:155_1_2_1"/>
<font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/><b>then reconsider </b><font color="Maroon">A</font> = <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font> as  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a>  ;<br/><b>consider </b><font color="Maroon">z1</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>;<br/><b>reconsider </b><font color="Maroon">zz</font> = <font color="Maroon">z1</font> as    <a href="hidden.html#M1">set</a>  ;<br/><b>take </b><font color="Maroon">zz</font> = <font color="Maroon">zz</font>;<br/><b>thus </b><a NAME="E6:155_1_2_1"/>
<font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">zz</font></span><a href="tarski.html#K1">}</a></span>
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_2_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">y</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:155_1_2_1_1"/><i><font color="Green">E46</font></i>: 
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font>
 ;<br/>

<a NAME="E2:155_1_2_1_1"/>
2 <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<a NAME="E3:155_1_2_1_1"/><b>then </b>
( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y</font>,2</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,2</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font></span>)</span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">2</span><a href="tarski.html#K1">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span> )
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T24" target="_self">Th24</a>, <a class="ref" href="zfmisc_1.html#T106">ZFMISC_1:106</a></i>;<br/>
<a NAME="E4:155_1_2_1_1"/><b>then </b>
( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y</font>,2</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,2</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> )
 
<b>by </b><i>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<a NAME="E5:155_1_2_1_1"/><b>then </b>
<font color="Maroon">y</font> <a href="hidden.html#R1">=</a> <font color="Maroon">z1</font>
 
<b>by </b><i><a class="ref" href="zfmisc_1.html#T33">ZFMISC_1:33</a></i>;<br/>
<b>hence </b><a NAME="E6:155_1_2_1_1"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">zz</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>


</div><b>end;</b></div></div><b>end;</b></div><b>hence </b><a NAME="E9:155_1_2"/>
 ex <font color="Olive">z</font> being   <a href="hidden.html#M1">set</a>  st <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">b</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Olive">z</font></span><a href="tarski.html#K1">}</a></span>
 ;<br/></div><b>end;</b></div>
<b>then reconsider </b><font color="Maroon">x2</font> = <font color="Maroon">x2</font> as    <a href="subset_1.html#M1">Element</a> of  <a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font> <b>by </b><i>, <a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_1_3"><b>now </b></a><div class="add"><b>thus </b><a NAME="E1:155_1_3"/>
( <font color="Maroon">x1</font> <a href="hidden.html#R2">in</a>  <a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font> &amp; <font color="Maroon">x2</font> <a href="hidden.html#R2">in</a>  <a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font> )
 ;<br/><b>assume </b><a NAME="E2:155_1_3"/>
( <font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">x2</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 ;<br/><b>then reconsider </b><font color="Maroon">x1</font> = <font color="Maroon">x1</font>, <font color="Maroon">x2</font> = <font color="Maroon">x2</font> as  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a>  ;<br/><b>consider </b><font color="Maroon">y1</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">x1</font>, <font color="Maroon">y2</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">x2</font>;<br/><a NAME="E5:155_1_3"/>
(  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C1</font> &amp;  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C2</font> )
 <b>by </b><i><a class="ref" href="cohsp_1.html#D10" target="_self">Def10</a></i>;<br/><a NAME="E6:155_1_3"/><b>then </b>
( <font color="Maroon">y1</font> <a href="hidden.html#R2">in</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C1</font> &amp; <font color="Maroon">y2</font> <a href="hidden.html#R2">in</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C2</font> )
 <b>by </b><i><a class="ref" href="tarski.html#D4">TARSKI:def 4</a></i>;<br/><a NAME="E7:155_1_3"/><b>then </b>
( <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span> <a href="hidden.html#R2">in</a> <font color="Maroon">C1</font> &amp; <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span> <a href="hidden.html#R2">in</a> <font color="Maroon">C2</font> )
 <b>by </b><i><a class="ref" href="coh_sp.html#T4">COH_SP:4</a></i>;<br/><a NAME="E8:155_1_3"/><b>then </b>
<span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span> <a href="hidden.html#R2">in</a> <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>
 ;<br/><b>then consider </b><font color="Maroon">z</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E10:155_1_3"/><i><font color="Green">E62</font></i>: 
<font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <span class="p1">(<span class="default"><span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, <a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/><a NAME="E11:155_1_3"/>
( <font color="Maroon">y1</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span> &amp; <font color="Maroon">y2</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><a NAME="E12:155_1_3"/><b>then </b>
( <font color="Maroon">y1</font> <a href="hidden.html#R2">in</a> <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span> &amp; <font color="Maroon">y2</font> <a href="hidden.html#R2">in</a> <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span> )
 <b>by </b><i><a class="ref" href="xboole_0.html#D3">XBOOLE_0:def 3</a></i>;<br/><a NAME="E13:155_1_3"/><b>then </b>
( <span class="p1">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y1</font>,1</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span></span>)</span> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y2</font>,2</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y1</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">y2</font></span><a href="tarski.html#K1">}</a></span></span>)</span> )
 <b>by </b><i>, , <a class="ref" href="cohsp_1.html#D15" target="_self">Def15</a>, <a class="ref" href="cohsp_1.html#D16" target="_self">Def16</a>, </i>;<br/><a NAME="E14:155_1_3"/><b>then </b>
( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y1</font>,1</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> &amp; <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">y2</font>,2</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> &amp; 1 <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> 2 )
 <b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><b>hence </b><a NAME="E15:155_1_3"/>
contradiction
 <b>by </b><i><a class="ref" href="zfmisc_1.html#T33">ZFMISC_1:33</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E11:155_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font></span>)</span> <a href="cohsp_1.html#K16" target="_self">"\/"</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font></span>)</span>
 <b>by </b><i>, </i>;<br/>


</div><b>end;</b></div>

<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E2:155"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font></span>)</span> <a href="cohsp_1.html#K16" target="_self">"\/"</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font></span>)</span>
 ;<br/>

<b>then consider </b><font color="Maroon">x1</font> being    <a href="subset_1.html#M1">Element</a> of  <a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font>, <font color="Maroon">x2</font> being    <a href="subset_1.html#M1">Element</a> of  <a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font><b> such that </b><br/><a NAME="E4:155"/><i><font color="Green">E63</font></i>: 
( <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x1</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">x2</font> &amp; ( <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  or <font color="Maroon">x2</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  ) )
 <b>by </b><i/>;<br/>
<a NAME="E5:155"/>
( <font color="Maroon">x1</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C1</font></span>)</span> &amp; <font color="Maroon">x2</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><a href="cohsp_1.html#K13" target="_self">'not'</a> <font color="Maroon">C2</font></span>)</span> )
 
<b>by </b><i><a class="ref" href="zfmisc_1.html#T92">ZFMISC_1:92</a></i>;<br/>
<a NAME="E6:155"/><b>then </b>
( <font color="Maroon">x1</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C1</font> &amp; <font color="Maroon">x2</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <font color="Maroon">C2</font> )
 
<b>by </b><i><a class="ref" href="cohsp_1.html#D10" target="_self">Def10</a></i>;<br/>
<a NAME="E7:155"/><b>then </b>
<font color="Maroon">x</font> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="tarski.html#K3">union</a> <font color="Maroon">C1</font></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><a href="tarski.html#K3">union</a> <font color="Maroon">C2</font></span>)</span>
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, <a class="ref" href="cohsp_1.html#T20" target="_self">Th20</a></i>;<br/>
<a NAME="E8:155"/><b>then </b><i><font color="Green">E80</font></i>: 
<font color="Maroon">x</font> <a href="tarski.html#R1">c=</a>  <a href="tarski.html#K3">union</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font></span>)</span>
 
<b>by </b><i/>;<br/>
<a NAME="E9:155"/>
for <font color="Olive">a</font> being   <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>  ex <font color="Olive">z</font> being   <a href="hidden.html#M1">set</a>  st <font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <font color="Olive">a</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Olive">z</font></span><a href="tarski.html#K1">}</a></span>
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="155_2"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">a</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font>;<br/>

<b>consider </b><font color="Maroon">a1</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C1</font>, <font color="Maroon">a2</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C2</font><b> such that </b><br/><a NAME="E2:155_2"/><i><font color="Green">E81</font></i>: 
<font color="Maroon">a</font> <a href="hidden.html#R1">=</a> <font color="Maroon">a1</font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">a2</font>
 <b>by </b><i/>;<br/>
<a NAME="E3:155_2"/><i><font color="Green">E83</font></i>: 
<font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a1</font></span>)</span> <a href="cohsp_1.html#K14" target="_self">U+</a> <span class="p1">(<span class="default"><font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a2</font></span>)</span>
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, , <a class="txt" href="cohsp_1.html#E2:155_2"><i><font color="Green">E81</font></i></a></i>;<br/>
<b>consider </b><font color="Maroon">z1</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E5:155_2"/><i><font color="Green">E84</font></i>: 
<font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a1</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z1</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<b>consider </b><font color="Maroon">z2</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E7:155_2"/><i><font color="Green">E85</font></i>: 
<font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a2</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z2</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<a NAME="E8:155_2"/>
( <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  or <font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 
;<br/>
<b>then consider </b><font color="Maroon">z</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E10:155_2"/><i><font color="Green">E86</font></i>: 
( ( <font color="Maroon">z</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z2</font>,2</span><a href="tarski.html#K4">]</a></span> &amp; <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  ) or ( <font color="Maroon">z</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,1</span><a href="tarski.html#K4">]</a></span> &amp; <font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  ) )
 ;<br/>
<b>take </b>
<font color="Maroon">z</font>
;<br/>

<b>let </b><font color="Maroon">y</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E11:155_2"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">x</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a</font>
 ;<br/>

<a NAME="E12:155_2"/><b>then </b><i><font color="Green">E91</font></i>: 
( <font color="Maroon">y</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">y</font> <a href="mcart_1.html#K1">`1</a> </span>)</span>,<span class="p2">(<span class="default"><font color="Maroon">y</font> <a href="mcart_1.html#K2">`2</a> </span>)</span></span><a href="tarski.html#K4">]</a></span> &amp; ( ( <font color="Maroon">y</font> <a href="mcart_1.html#K2">`2</a>  <a href="hidden.html#R1">=</a> 1 &amp; <font color="Maroon">y</font> <a href="mcart_1.html#K1">`1</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">x1</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a1</font> ) or ( <font color="Maroon">y</font> <a href="mcart_1.html#K2">`2</a>  <a href="hidden.html#R1">=</a> 2 &amp; <font color="Maroon">y</font> <a href="mcart_1.html#K1">`1</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">x2</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">a2</font> ) ) )
 
<b>by </b><i>, <a class="ref" href="cohsp_1.html#D14" target="_self">Def14</a></i>;<br/>
<div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="155_2_1"><b>per </b></a><a class="txt" onclick="hs(this)" href="javascript:()"><b>cases </b></a><span class="hide"><a NAME="E1:155_2_1"/>
( ( <font color="Maroon">z</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z2</font>,2</span><a href="tarski.html#K4">]</a></span> &amp; <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  ) or ( <font color="Maroon">z</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,1</span><a href="tarski.html#K4">]</a></span> &amp; <font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  ) )
 </span><b>by </b><i><a class="ref" href="cohsp_1.html#D17" target="_self">Def17</a></i>;<br/><div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="155_2_1_1"><b>suppose </b></a><a NAME="E1:155_2_1_1"/><i><font color="Green">E118</font></i>: 
( <font color="Maroon">z</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z2</font>,2</span><a href="tarski.html#K4">]</a></span> &amp; <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  )
 ;<br/><div class="add"><a NAME="E2:155_2_1_1"/><b>then </b>
<font color="Maroon">y</font> <a href="mcart_1.html#K1">`1</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">z2</font>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T24" target="_self">Th24</a>, <a class="ref" href="cohsp_1.html#T25" target="_self">Th25</a>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><b>hence </b><a NAME="E3:155_2_1_1"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T25" target="_self">Th25</a>, , <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/></div><b>end;</b></div><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="155_2_1_2"><b>suppose </b></a><a NAME="E1:155_2_1_2"/><i><font color="Green">E119</font></i>: 
( <font color="Maroon">z</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">z1</font>,1</span><a href="tarski.html#K4">]</a></span> &amp; <font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 ;<br/><div class="add"><a NAME="E2:155_2_1_2"/><b>then </b>
<font color="Maroon">y</font> <a href="mcart_1.html#K1">`1</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">z1</font>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, <a class="txt" href="cohsp_1.html#E12:155_2"><i><font color="Green">E91</font></i></a>, <a class="ref" href="cohsp_1.html#T25" target="_self">Th25</a>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><b>hence </b><a NAME="E3:155_2_1_2"/>
<font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">z</font></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i><a class="ref" href="cohsp_1.html#T23" target="_self">Th23</a>, <a class="ref" href="cohsp_1.html#T25" target="_self">Th25</a>, , <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/></div><b>end;</b></div></div><b>end;</b></div>

</div><b>end;</b></div>
<b>hence </b><a NAME="E10:155"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="cohsp_1.html#K13" target="_self">'not'</a> <span class="p1">(<span class="default"><font color="Maroon">C1</font> <a href="cohsp_1.html#K15" target="_self">"/\"</a> <font color="Maroon">C2</font></span>)</span>
 <b>by </b><i/>;<br/>


</div>
