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

<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>assume </b><a NAME="E1:3_1_1"/><i><font color="Green">E18</font></i>: 
<font color="Maroon">X</font> is <a href="membered.html#V5" target="_self">natural-membered</a>
 ;<br/>

<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="membered.html#D4" target="_self">MEMBERED:def 4</a><br/>

<b>assume </b><a NAME="E2:3_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X</font>
 ;<br/>

<a NAME="E3:3_1_1"/><b>then </b>
<font color="Maroon">x</font> is <a href="ordinal1.html#V7">natural</a>
 
<b>by </b><i>, </i>;<br/>
<a NAME="E4:3_1_1"/><b>then </b>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="ordinal1.html#K5">omega</a> 
 
<b>by </b><i><a class="ref" href="ordinal1.html#D13">ORDINAL1:def 13</a></i>;<br/>
<b>hence </b><a NAME="E5:3_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="numbers.html#K4">INT</a> 
 <b>by </b><i><a class="ref" href="numbers.html#T17">NUMBERS:17</a></i>; <i><font color="Red">:: according to </font></i><a class="ref" href="int_1.html#D2">INT_1:def 2</a><br/>


</div>
