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<b>let </b><font color="Maroon" title="c1">x</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>

<b>assume </b><a NAME="E1:37_1_1"/><i><font color="Green" title="E23">A1</font></i>: 
<font color="Maroon" title="c1">x</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>
 ;<br/>

<b>given </b><font color="Maroon" title="c2">a</font>, <font color="Maroon" title="c3">b</font> being    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> <b> such that </b><a NAME="E3:37_1_1"/><i><font color="Green" title="E24">A2</font></i>: 
<font color="Maroon" title="c1">x</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1"><a href="tarski.html#K4" title="TARSKI:func.4">[</a><span class="default"><font color="Maroon" title="c2">a</font>,<font color="Maroon" title="c3">b</font></span><a href="tarski.html#K4" title="TARSKI:func.4">]</a></span>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="facirc_1.html#D1" title="FACIRC_1:def.1">FACIRC_1:def 1</a><br/>

<b>thus </b><a NAME="E4:37_1_1"/>
contradiction
 <b>by </b><i><a class="txt" href="facirc_2.html#E1:37_1_1"><i><font color="Green" title="E23">A1</font></i></a>, <a class="txt" href="facirc_2.html#E3:37_1_1"><i><font color="Green" title="E24">A2</font></i></a></i>;<br/>


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