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

<b>let </b><font color="Maroon">L</font> be   <a href="robbins1.html#NM1">preOrthoLattice</a>;<br/>

<b>assume </b><a NAME="E1:63_1_1"/>
( <font color="Maroon">L</font> is <a href="robbins2.html#V1" target="_self">satisfying_DN_1</a> &amp; <font color="Maroon">L</font> is <a href="robbins1.html#V9">de_Morgan</a> )
 ;<br/>

<b>then reconsider </b><font color="Maroon">L'</font> = <font color="Maroon">L</font> as  <a href="robbins1.html#V9">de_Morgan</a> <a href="robbins2.html#V1" target="_self">satisfying_DN_1</a> <a href="robbins1.html#NM1">preOrthoLattice</a> ;<br/>
<a NAME="E3:63_1_1"/>
<font color="Maroon">L'</font> is <a href="lattices.html#V17">Boolean</a>
 
;<br/>
<b>hence </b><a NAME="E4:63_1_1"/>
<font color="Maroon">L</font> is <a href="lattices.html#V17">Boolean</a>
 ;<br/>


</div>
