<?xml version="1.0"?>
<div class="add">

<b>consider </b><font color="Maroon">p1</font> being    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">D1</font>, <font color="Maroon">p2</font> being    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">D2</font>;<br/>
<b>set </b><font color="Maroon">X</font> = <span class="p1">{<span class="default"> <span class="p2">(<span class="default"><font color="Olive">p</font> <a href="lattices.html#K3">"\/"</a> <font color="Olive">q</font></span>)</span> where <font color="Olive">p</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>, <font color="Olive">q</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> : ( <font color="Olive">p</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D1</font> &amp; <font color="Olive">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D2</font> ) </span>}</span> ;<br/>
<a NAME="E2:67_1_1"/>
<font color="Maroon">p1</font> <a href="lattices.html#K3">"\/"</a> <font color="Maroon">p2</font> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <span class="p2">(<span class="default"><font color="Olive">p</font> <a href="lattices.html#K3">"\/"</a> <font color="Olive">q</font></span>)</span> where <font color="Olive">p</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>, <font color="Olive">q</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> : ( <font color="Olive">p</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D1</font> &amp; <font color="Olive">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D2</font> ) </span>}</span> 
 
;<br/>
<b>then reconsider </b><font color="Maroon">X</font> = <span class="p1">{<span class="default"> <span class="p2">(<span class="default"><font color="Olive">p</font> <a href="lattices.html#K3">"\/"</a> <font color="Olive">q</font></span>)</span> where <font color="Olive">p</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>, <font color="Olive">q</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> : ( <font color="Olive">p</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D1</font> &amp; <font color="Olive">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D2</font> ) </span>}</span>  as  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a>  ;<br/>
<a NAME="E4:67_1_1"/>
<font color="Maroon">X</font> <a href="hidden.html#R1">=</a> <font color="Maroon">D1</font> <a href="filter_2.html#K20" target="_self">"\/"</a> <font color="Maroon">D2</font>
 
;<br/>
<b>hence </b><a NAME="E5:67_1_1"/>
not <font color="Maroon">D1</font> <a href="filter_2.html#K20" target="_self">"\/"</a> <font color="Maroon">D2</font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/>


</div>
