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

<b>let </b><font color="Maroon">a</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:128"/>
<font color="Maroon">a</font> <a href="hidden.html#R2">in</a>  <a href="zf_lang.html#K9">WFF</a> 
 ;<br/>

<b>then reconsider </b><font color="Maroon">H</font> = <font color="Maroon">a</font> as   <a href="zf_lang.html#NM2">ZF-formula</a> <b>by </b><i><a class="ref" href="zf_lang.html#T14">ZF_LANG:14</a></i>;<br/>
<a NAME="E3:128"/>
( <font color="Maroon">H</font> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><a href="numbers.html#K5">NAT</a> ,<a href="numbers.html#K5">NAT</a> </span><a href="zfmisc_1.html#K2">:]</a></span> &amp; <font color="Maroon">H</font> <a href="hidden.html#R1">=</a> <font color="Maroon">H</font> )
 
;<br/>
<b>hence </b><a NAME="E4:128"/>
<font color="Maroon">a</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><a href="numbers.html#K5">NAT</a> ,<a href="numbers.html#K5">NAT</a> </span><a href="zfmisc_1.html#K2">:]</a></span>
 ;<br/>


</div>
