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

<b>take </b>
 <a href="xboole_0.html#K1">{}</a> 
;<br/>

<a NAME="E1:21_1_1"/>
 <a href="xboole_0.html#K1">{}</a>  is <a href="card_3.html#V1">Cardinal-yielding</a>
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="21_1_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="card_3.html#D1">CARD_3:def 1</a><br/>

<b>thus </b><a NAME="E1:21_1_1_1"/>
(  not <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <a href="xboole_0.html#K1">{}</a>  or <a href="xboole_0.html#K1">{}</a>  <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> is    <a href="hidden.html#M1">set</a>  )
 ;<br/>


</div><b>end;</b></div>
<b>hence </b><a NAME="E2:21_1_1"/>
 <a href="xboole_0.html#K1">{}</a>  is <a href="card_3.html#V1">Cardinal-yielding</a>
 ;<br/>


</div>
