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<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Si</font> be   <a href="prob_1.html#NM3">SigmaField</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">XSeq</font> be    <a href="prob_1.html#M1">SetSequence</a> of <font color="Maroon">Si</font>;<br/>





<b>assume </b><a NAME="E1:28"/><i><font color="Green">E24</font></i>: 
<font color="Maroon">XSeq</font> is <a href="prob_1.html#V3">non-decreasing</a>
 ;<br/>

<a NAME="E2:28"/>
 <a href="prob_3.html#K5">@Partial_Union</a> <font color="Maroon">XSeq</font> <a href="funct_2.html#R2">=</a>  <a href="prob_3.html#K2">Partial_Union</a> <font color="Maroon">XSeq</font>
 
<b>by </b><i><a class="ref" href="prob_3.html#D6">PROB_3:def 6</a></i>;<br/>
<b>hence </b><a NAME="E3:28"/>
 <a href="prob_3.html#K5">@Partial_Union</a> <font color="Maroon">XSeq</font> <a href="funct_2.html#R2">=</a> <font color="Maroon">XSeq</font>
 <b>by </b><i>, </i>;<br/>


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