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

<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="nat_1.html#NM1">Nat</a>;<br/>

<a NAME="E1:23"/>
( not <font color="Maroon">c<sub>1</sub></font> is <a href="abian.html#V1">even</a> iff  not <font color="Maroon">c<sub>1</sub></font> <a href="nat_1.html#K4">mod</a> 2 <a href="hidden.html#R1">=</a> 0 )
 
<b>by </b><i><a class="ref" href="nat_2.html#T23" target="_self">Th23</a></i>;<br/>
<b>hence </b><a NAME="E2:23"/>
( not <font color="Maroon">c<sub>1</sub></font> is <a href="abian.html#V1">even</a> iff <font color="Maroon">c<sub>1</sub></font> <a href="nat_1.html#K4">mod</a> 2 <a href="hidden.html#R1">=</a> 1 )
 <b>by </b><i><a class="ref" href="nat_1.html#T62">NAT_1:62</a></i>;<br/>


</div>
