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<b>let </b><font color="Maroon">x</font> be  <a href="xreal_0.html#V1">real</a>  <a href="ordinal1.html#NM1" target="_self">number</a> ;<br/><b>let </b><font color="Maroon">y</font> be  <a href="xreal_0.html#V1">real</a>  <a href="ordinal1.html#NM1" target="_self">number</a> ;<br/>



<b>assume </b><a NAME="E1:18"/><i><font color="Green">E20</font></i>: 
( 0 <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">x</font> &amp; 0 <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">y</font> )
 ;<br/>

<b>assume </b><a NAME="E2:18"/>
<font color="Maroon">x</font> <a href="square_1.html#K3" target="_self">^2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">y</font> <a href="square_1.html#K3" target="_self">^2</a> 
 ;<br/>

<a NAME="E3:18"/><b>then </b>
( <font color="Maroon">x</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">y</font> &amp; <font color="Maroon">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">x</font> )
 
<b>by </b><i><a class="txt" href="square_1.html#E3"><i><font color="Green">Lemma22</font></i></a>, <a class="txt" href="square_1.html#E1:18"><i><font color="Green">E20</font></i></a></i>;<br/>
<b>hence </b><a NAME="E4:18"/>
<font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">y</font>
 <b>by </b><i><a class="ref" href="xxreal_0.html#T1">XXREAL_0:1</a></i>;<br/>


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