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<b>assume </b><a NAME="E1:20"/><i><font color="Green">E18</font></i>: 
 <a href="xxreal_0.html#K2" target="_self">-infty</a>  <a href="hidden.html#R2">in</a>  <a href="numbers.html#K1">REAL</a> 
 ;<br/>

<a NAME="E2:20"/><i><font color="Green">E19</font></i>: 
<span class="p1"><a href="tarski.html#K2">{</a><span class="default">0,<a href="numbers.html#K1">REAL</a> </span><a href="tarski.html#K2">}</a></span> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><span class="p2"><a href="tarski.html#K2">{</a><span class="default">0,<a href="numbers.html#K1">REAL</a> </span><a href="tarski.html#K2">}</a></span>,<span class="p2"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span></span><a href="tarski.html#K2">}</a></span>
 
<b>by </b><i><a class="ref" href="tarski.html#D2">TARSKI:def 2</a></i>;<br/>
<a NAME="E3:20"/>
 <a href="numbers.html#K1">REAL</a>  <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default">0,<a href="numbers.html#K1">REAL</a> </span><a href="tarski.html#K2">}</a></span>
 
<b>by </b><i><a class="ref" href="tarski.html#D2">TARSKI:def 2</a></i>;<br/>
<b>hence </b><a NAME="E4:20"/>
contradiction
 <b>by </b><i><a class="txt" href="xxreal_0.html#E1:20"><i><font color="Green">E18</font></i></a>, <a class="txt" href="xxreal_0.html#E2:20"><i><font color="Green">E19</font></i></a>, <a class="ref" href="ordinal1.html#T3">ORDINAL1:3</a></i>;<br/>


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