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

<b>thus </b><a NAME="E1:25"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <font color="Olive">k</font> where <font color="Olive">k</font> is    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a>  : ( 2,<font color="Olive">k</font> <a href="int_2.html#R2">are_relative_prime</a>  &amp; <font color="Olive">k</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1 &amp; <font color="Olive">k</font> <a href="xxreal_0.html#R1">&lt;=</a> 2 ) </span>}</span>  implies <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> 1 )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="25_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:25_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <font color="Olive">k</font> where <font color="Olive">k</font> is    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a>  : ( 2,<font color="Olive">k</font> <a href="int_2.html#R2">are_relative_prime</a>  &amp; <font color="Olive">k</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1 &amp; <font color="Olive">k</font> <a href="xxreal_0.html#R1">&lt;=</a> 2 ) </span>}</span> 
 ;<br/>

<b>then consider </b><font color="Maroon">k</font> being    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a> <b> such that </b><br/><a NAME="E3:25_1"/><i><font color="Green">E30</font></i>: 
<font color="Maroon">k</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font>
 <b>and </b><br/><a NAME="E4:25_1"/><i><font color="Green">E31</font></i>: 
2,<font color="Maroon">k</font> <a href="int_2.html#R2">are_relative_prime</a> 
 <b>and </b><br/><a NAME="E5:25_1"/><i><font color="Green">E34</font></i>: 
( <font color="Maroon">k</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1 &amp; <font color="Maroon">k</font> <a href="xxreal_0.html#R1">&lt;=</a> 2 )
 ;<br/>
<a NAME="E6:25_1"/><i><font color="Green">E44</font></i>: 
( <font color="Maroon">k</font> <a href="hidden.html#R1">=</a> 1 or <font color="Maroon">k</font> <a href="hidden.html#R1">=</a> 2 )
 
<b>by </b><i><a class="txt" href="euler_1.html#E1"><i><font color="Green">Lemma27</font></i></a>, <a class="ref" href="cqc_the1.html#T3">CQC_THE1:3</a></i>;<br/>
<a NAME="E7:25_1"/>
2 <a href="nat_1.html#K10">hcf</a> 2 <a href="hidden.html#R1">=</a> 2
 
;<br/>
<b>hence </b><a NAME="E8:25_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> 1
 <b>by </b><i>, , <a class="txt" href="euler_1.html#E2"><i><font color="Green">Lemma28</font></i></a>, <a class="ref" href="int_2.html#D6">INT_2:def 6</a></i>;<br/>


</div><b>end;</b></div>

<a NAME="E2:25"/>
2 <a href="nat_1.html#K10">hcf</a> 1 <a href="hidden.html#R1">=</a> 1
 
<b>by </b><i><a class="ref" href="newton.html#T64">NEWTON:64</a></i>;<br/>
<a NAME="E3:25"/><b>then </b>
2,1 <a href="int_2.html#R2">are_relative_prime</a> 
 
<b>by </b><i><a class="ref" href="int_2.html#D6">INT_2:def 6</a></i>;<br/>
<b>hence </b><a NAME="E4:25"/>
( <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> 1 implies <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <font color="Olive">k</font> where <font color="Olive">k</font> is    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a>  : ( 2,<font color="Olive">k</font> <a href="int_2.html#R2">are_relative_prime</a>  &amp; <font color="Olive">k</font> <a href="xxreal_0.html#NR2" target="_self">&gt;=</a> 1 &amp; <font color="Olive">k</font> <a href="xxreal_0.html#R1">&lt;=</a> 2 ) </span>}</span>  )
 ;<br/>


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