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

<b>let </b><font color="Maroon">L</font> be   <a href="lattices.html#NM1">Lattice</a>;<br/><b>let </b><font color="Maroon">p</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>;<br/><b>let </b><font color="Maroon">q</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>;<br/><b>let </b><font color="Maroon">r</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>;<br/>







<b>assume </b><a NAME="E1:89"/>
<font color="Maroon">p</font> <a href="lattices.html#R3">[=</a> <font color="Maroon">q</font>
 ;<br/>

<a NAME="E2:89"/><b>then </b>
<span class="p1"><a href="filter_2.html#K22" target="_self">[#</a><span class="default"><font color="Maroon">p</font>,<font color="Maroon">q</font></span><a href="filter_2.html#K22" target="_self">#]</a></span> <a href="hidden.html#R1">=</a> <span class="p1">{<span class="default"> <font color="Olive">s</font> where <font color="Olive">s</font> is   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> : ( <font color="Maroon">p</font> <a href="lattices.html#R3">[=</a> <font color="Olive">s</font> &amp; <font color="Olive">s</font> <a href="lattices.html#R3">[=</a> <font color="Maroon">q</font> ) </span>}</span> 
 
<b>by </b><i/>;<br/>
<a NAME="E3:89"/><b>then </b>
( <font color="Maroon">r</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="filter_2.html#K22" target="_self">[#</a><span class="default"><font color="Maroon">p</font>,<font color="Maroon">q</font></span><a href="filter_2.html#K22" target="_self">#]</a></span> iff  ex <font color="Olive">s</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> st <br/>( <font color="Maroon">r</font> <a href="hidden.html#R1">=</a> <font color="Olive">s</font> &amp; <font color="Maroon">p</font> <a href="lattices.html#R3">[=</a> <font color="Olive">s</font> &amp; <font color="Olive">s</font> <a href="lattices.html#R3">[=</a> <font color="Maroon">q</font> ) )
 
;<br/>
<b>hence </b><a NAME="E4:89"/>
( <font color="Maroon">r</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="filter_2.html#K22" target="_self">[#</a><span class="default"><font color="Maroon">p</font>,<font color="Maroon">q</font></span><a href="filter_2.html#K22" target="_self">#]</a></span> iff ( <font color="Maroon">p</font> <a href="lattices.html#R3">[=</a> <font color="Maroon">r</font> &amp; <font color="Maroon">r</font> <a href="lattices.html#R3">[=</a> <font color="Maroon">q</font> ) )
 ;<br/>


</div>
