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<b>let </b><font color="Maroon">X</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">PX</font> be    <a href="eqrel_1.html#M1">a_partition</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">Pi</font> be    <a href="hidden.html#M1">set</a> ;<br/>





<b>assume </b><a NAME="E1:7"/>
<font color="Maroon">Pi</font> <a href="hidden.html#R2">in</a> <font color="Maroon">PX</font>
 ;<br/>

<b>then reconsider </b><font color="Maroon">Pi</font> = <font color="Maroon">Pi</font> as    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">PX</font> ;<br/>
<a NAME="E3:7"/><i><font color="Green">E22</font></i>: 
<font color="Maroon">Pi</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="eqrel_1.html#D6">EQREL_1:def 6</a></i>;<br/>
<b>consider </b><font color="Maroon">q</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">Pi</font>;<br/>
<a NAME="E5:7"/>
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Pi</font>
 
<b>by </b><i/>;<br/>
<b>then reconsider </b><font color="Maroon">q</font> = <font color="Maroon">q</font> as    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">X</font> ;<br/>
<b>take </b>
<font color="Maroon">q</font>
;<br/>

<b>thus </b><a NAME="E7:7"/>
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Pi</font>
 <b>by </b><i/>;<br/>


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