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

<b>assume </b><a NAME="E1:3"/><i><font color="Green">E28</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="numbers.html#K3">RAT</a> 
 ;<br/>

<a NAME="E2:3"/><b>then </b><i><font color="Green">E29</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <a href="arytm_3.html#K7">RAT+</a>  <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span>,<a href="arytm_3.html#K7">RAT+</a> </span><a href="zfmisc_1.html#K2">:]</a></span>
 
<b>by </b><i><a class="ref" href="numbers.html#D3">NUMBERS:def 3</a></i>;<br/>
<div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="3_1"><b>per </b></a><a class="txt" onclick="hs(this)" href="javascript:()"><b>cases </b></a><span class="hide"><a NAME="E1:3_1"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="arytm_3.html#K7">RAT+</a>  or <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span>,<a href="arytm_3.html#K7">RAT+</a> </span><a href="zfmisc_1.html#K2">:]</a></span> )
 </span><b>by </b><i>, <a class="ref" href="xboole_0.html#D2">XBOOLE_0:def 2</a></i>;<br/><div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="3_1_1"><b>suppose </b></a><a NAME="E1:3_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="arytm_3.html#K7">RAT+</a> 
 ;<br/><div class="add"><b>then reconsider </b><font color="Maroon">x</font> = <font color="Maroon">x</font> as    <a href="subset_1.html#M1">Element</a> of  <a href="arytm_3.html#K7">RAT+</a>  ;<br/><b>take </b>
 <a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x</font>
;<br/><b>take </b>
 <a href="arytm_3.html#K9">denominator</a> <font color="Maroon">x</font>
;<br/><a NAME="E3:3_1_1"/>
 <a href="arytm_3.html#NK11" target="_self">quotient</a> <span class="p1">(<span class="default"><a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x</font></span>)</span>,<span class="p1">(<span class="default"><a href="arytm_3.html#K9">denominator</a> <font color="Maroon">x</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font>
 <b>by </b><i><a class="ref" href="arytm_3.html#T45">ARYTM_3:45</a></i>;<br/><b>hence </b><a NAME="E4:3_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x</font></span>)</span> <a href="xcmplx_0.html#K7">/</a> <span class="p1">(<span class="default"><a href="arytm_3.html#K9">denominator</a> <font color="Maroon">x</font></span>)</span>
 <b>by </b><i/>;<br/></div><b>end;</b></div><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="3_1_2"><b>suppose </b></a><a NAME="E1:3_1_2"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><span class="p2"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span>,<a href="arytm_3.html#K7">RAT+</a> </span><a href="zfmisc_1.html#K2">:]</a></span>
 ;<br/><div class="add"><b>then consider </b><font color="Maroon">x1</font> being    <a href="hidden.html#M1">set</a> , <font color="Maroon">x2</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E3:3_1_2"/><i><font color="Green">E34</font></i>: 
<font color="Maroon">x1</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default">0</span><a href="tarski.html#K1">}</a></span>
 <b>and </b><br/><a NAME="E4:3_1_2"/><i><font color="Green">E35</font></i>: 
<font color="Maroon">x2</font> <a href="hidden.html#R2">in</a>  <a href="arytm_3.html#K7">RAT+</a> 
 <b>and </b><br/><a NAME="E5:3_1_2"/><i><font color="Green">E36</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font></span><a href="tarski.html#K4">]</a></span>
 <b>by </b><i><a class="ref" href="zfmisc_1.html#T103">ZFMISC_1:103</a></i>;<br/><b>reconsider </b><font color="Maroon">x2</font> = <font color="Maroon">x2</font> as    <a href="subset_1.html#M1">Element</a> of  <a href="arytm_3.html#K7">RAT+</a>  <b>by </b><i/>;<br/><b>reconsider </b><font color="Maroon">x'</font> = <font color="Maroon">x2</font> as    <a href="subset_1.html#M1">Element</a> of  <a href="arytm_2.html#K2">REAL+</a>  <b>by </b><i>, <a class="ref" href="arytm_2.html#T1">ARYTM_2:1</a></i>;<br/><b>take </b><font color="Maroon">m</font> =  <a href="xcmplx_0.html#K4">-</a> <span class="p1">(<span class="default"><a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x2</font></span>)</span>;<br/><b>take </b><font color="Maroon">n</font> =  <a href="arytm_3.html#K9">denominator</a> <font color="Maroon">x2</font>;<br/><i><font color="Green">E37</font></i>: <font color="Maroon">x2</font> = 
 <a href="arytm_3.html#NK11" target="_self">quotient</a> <span class="p1">(<span class="default"><a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x2</font></span>)</span>,<span class="p1">(<span class="default"><a href="arytm_3.html#K9">denominator</a> <font color="Maroon">x2</font></span>)</span>
<b>by </b><i><a class="ref" href="arytm_3.html#T45">ARYTM_3:45</a></i>
<br/>.= 
<span class="p1">(<span class="default"><a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x2</font></span>)</span> <a href="xcmplx_0.html#K7">/</a> <font color="Maroon">n</font>
<b>by </b><i/>
;<br/><a NAME="E9:3_1_2"/><i><font color="Green">E38</font></i>: 
<font color="Maroon">x1</font> <a href="hidden.html#R1">=</a> 0
 <b>by </b><i>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><a NAME="E10:3_1_2"/><i><font color="Green">E39</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K4">[</a><span class="default">0,<font color="Maroon">x'</font></span><a href="tarski.html#K4">]</a></span>
 <b>by </b><i>, , <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><a NAME="E11:3_1_2"/>
not <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><span class="p2"><a href="tarski.html#K4">[</a><span class="default">0,0</span><a href="tarski.html#K4">]</a></span></span><a href="tarski.html#K1">}</a></span>
 <b>by </b><i>, <a class="ref" href="numbers.html#D3">NUMBERS:def 3</a>, <a class="ref" href="xboole_0.html#D4">XBOOLE_0:def 4</a></i>;<br/><a NAME="E12:3_1_2"/><b>then </b>
<font color="Maroon">x2</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> 0
 <b>by </b><i>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/><b>hence </b><font color="Maroon">x</font> = 
<font color="Maroon">0'</font> <a href="arytm_1.html#K2">-</a> <font color="Maroon">x'</font>
<b>by </b><i>, , <a class="ref" href="arytm_1.html#T19">ARYTM_1:19</a></i>
<br/>.= 
 <a href="xcmplx_0.html#K4">-</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="arytm_3.html#K8">numerator</a> <font color="Maroon">x2</font></span>)</span> <a href="xcmplx_0.html#K7">/</a> <font color="Maroon">n</font></span>)</span>
<b>by </b><i>, </i>
<br/>.= 
<font color="Maroon">m</font> <a href="xcmplx_0.html#K7">/</a> <font color="Maroon">n</font>

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

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