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<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>assume </b><a NAME="E1:37_1_1"/><i><font color="Green">E25</font></i>: 
<font color="Maroon">x</font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/>

<b>given </b><font color="Maroon">a</font> being    <a href="hidden.html#M1">set</a> , <font color="Maroon">b</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><a NAME="E2:37_1_1"/><i><font color="Green">E33</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">a</font>,<font color="Maroon">b</font></span><a href="tarski.html#K4">]</a></span>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="facirc_1.html#D1">FACIRC_1:def 1</a><br/>

<b>thus </b><a NAME="E3:37_1_1"/>
contradiction
 <b>by </b><i>, </i>;<br/>


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