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<b>let </b><font color="Maroon" title="c1">a</font> be   <a href="supinf_1.html#NM3" title="SUPINF_1:NM.3">R_eal</a>;<br/>

<b>thus </b><a NAME="E1:22"/>
<span class="p1"><a href="measure5.html#K4" title="MEASURE5:func.4">[.</a><span class="default"><font color="Maroon" title="c1">a</font>,<font color="Maroon" title="c1">a</font></span><a href="measure5.html#K4" title="MEASURE5:func.4">.[</a></span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="22_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:22_1"/><i><font color="Green" title="E15">A1</font></i>: 
not <span class="p1"><a href="measure5.html#K4" title="MEASURE5:func.4">[.</a><span class="default"><font color="Maroon" title="c1">a</font>,<font color="Maroon" title="c1">a</font></span><a href="measure5.html#K4" title="MEASURE5:func.4">.[</a></span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 ;<br/>

<b>consider </b><font color="Maroon" title="c2">x</font> being    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <span class="p1"><a href="measure5.html#K4" title="MEASURE5:func.4">[.</a><span class="default"><font color="Maroon" title="c1">a</font>,<font color="Maroon" title="c1">a</font></span><a href="measure5.html#K4" title="MEASURE5:func.4">.[</a></span>;<br/>
<b>reconsider </b><font color="Maroon" title="c3">x</font> = <font color="Maroon" title="c2">x</font> as   <a href="supinf_1.html#NM3" title="SUPINF_1:NM.3">R_eal</a> <b>by </b><i><a class="txt" href="measure5.html#E1:22_1"><i><font color="Green" title="E15">A1</font></i></a>, <a class="ref" href="measure5.html#T11" target="_self" title="MEASURE5:th.11">Th11</a></i>;<br/>
<a NAME="E4:22_1"/>
( <font color="Maroon" title="c1">a</font> <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon" title="c3">x</font> &amp; <font color="Maroon" title="c3">x</font> <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon" title="c1">a</font> &amp; <font color="Maroon" title="c3">x</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a> <font color="Maroon" title="c1">a</font> )
 
<b>by </b><i><a class="txt" href="measure5.html#E1:22_1"><i><font color="Green" title="E15">A1</font></i></a>, <a class="ref" href="measure5.html#D4" target="_self" title="MEASURE5:def.4">Def4</a></i>;<br/>
<b>hence </b><a NAME="E5:22_1"/>
contradiction
 <b>by </b><i><a class="ref" href="xxreal_0.html#T1" title="XXREAL_0:th.1">XXREAL_0:1</a></i>;<br/>


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

<b>assume </b><a NAME="E2:22"/><i><font color="Green" title="E15">A2</font></i>: 
not <span class="p1"><a href="measure5.html#K3" title="MEASURE5:func.3">].</a><span class="default"><font color="Maroon" title="c1">a</font>,<font color="Maroon" title="c1">a</font></span><a href="measure5.html#K3" title="MEASURE5:func.3">.]</a></span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 ;<br/>

<b>consider </b><font color="Maroon" title="c2">x</font> being    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <span class="p1"><a href="measure5.html#K3" title="MEASURE5:func.3">].</a><span class="default"><font color="Maroon" title="c1">a</font>,<font color="Maroon" title="c1">a</font></span><a href="measure5.html#K3" title="MEASURE5:func.3">.]</a></span>;<br/>
<b>reconsider </b><font color="Maroon" title="c3">x</font> = <font color="Maroon" title="c2">x</font> as   <a href="supinf_1.html#NM3" title="SUPINF_1:NM.3">R_eal</a> <b>by </b><i><a class="txt" href="measure5.html#E2:22"><i><font color="Green" title="E15">A2</font></i></a>, <a class="ref" href="measure5.html#T11" target="_self" title="MEASURE5:th.11">Th11</a></i>;<br/>
<a NAME="E5:22"/>
( <font color="Maroon" title="c1">a</font> <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon" title="c3">x</font> &amp; <font color="Maroon" title="c3">x</font> <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon" title="c1">a</font> &amp; <font color="Maroon" title="c3">x</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a> <font color="Maroon" title="c1">a</font> )
 
<b>by </b><i><a class="txt" href="measure5.html#E2:22"><i><font color="Green" title="E15">A2</font></i></a>, <a class="ref" href="measure5.html#D3" target="_self" title="MEASURE5:def.3">Def3</a></i>;<br/>
<b>hence </b><a NAME="E6:22"/>
contradiction
 <b>by </b><i><a class="ref" href="xxreal_0.html#T1" title="XXREAL_0:th.1">XXREAL_0:1</a></i>;<br/>


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