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<b>let </b><font color="Maroon">x1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x2</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">A</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/>





<b>assume </b><a NAME="E1:8"/><i><font color="Green">E38</font></i>: 
<font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">x2</font>
 ;<br/>

<b>let </b><font color="Maroon">y1</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>, <font color="Maroon">y2</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>;<br/>

<b>set </b><font color="Maroon">h</font> = <font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">y1</font>,<font color="Maroon">y2</font>;<br/>
<a NAME="E2:8"/>
( <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">y1</font>,<font color="Maroon">y2</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">y1</font> &amp; <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">y1</font>,<font color="Maroon">y2</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x2</font> <a href="hidden.html#R1">=</a> <font color="Maroon">y2</font> &amp; <font color="Maroon">x1</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font></span><a href="tarski.html#K2">}</a></span> &amp; <font color="Maroon">x2</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font></span><a href="tarski.html#K2">}</a></span> )
 
<b>by </b><i>, <a class="ref" href="funct_4.html#T66">FUNCT_4:66</a>, <a class="ref" href="tarski.html#D2">TARSKI:def 2</a></i>;<br/>
<b>hence </b><a NAME="E3:8"/>
( <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">y1</font>,<font color="Maroon">y2</font></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">y1</font> &amp; <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">y1</font>,<font color="Maroon">y2</font></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x2</font> <a href="hidden.html#R1">=</a> <font color="Maroon">y2</font> )
 <b>by </b><i/>;<br/>


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