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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="E1:8"/><i><font color="Green">E18</font></i>: 
<font color="Maroon">X</font> is <a href="membered.html#V2" target="_self">real-membered</a>
 ;<br/>

<b>let </b><font color="Maroon">x</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="E2:8"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X</font>
 ;<br/>

<a NAME="E3:8"/><b>then </b>
<font color="Maroon">x</font> is <a href="xreal_0.html#V1">real</a>
 
<b>by </b><i><a class="txt" href="membered.html#E1"><i><font color="Green">Lemma9</font></i></a>, </i>;<br/>
<b>hence </b><a NAME="E4:8"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="numbers.html#K1">REAL</a> 
 <b>by </b><i><a class="ref" href="xreal_0.html#D1">XREAL_0:def 1</a></i>;<br/>


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