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

<a NAME="E1:7_2_1"/>
 <a href="xboole_0.html#K1" target="_self">{}</a>  is <a href="xboole_0.html#V1" target="_self">empty</a>
 
;<br/>
<b>hence </b><a NAME="E2:7_2_1"/>
ex <font color="Olive">b<sub>1</sub></font> being   <a href="hidden.html#M1">set</a>  st <font color="Olive">b<sub>1</sub></font> is <a href="xboole_0.html#V1" target="_self">empty</a>
 ;<br/>


</div>
