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<b>let </b><font color="Maroon" title="c1">X</font> be  <a href="membered.html#V4" title="MEMBERED:attr.4">rational-membered</a>  <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>

<b>assume </b><a NAME="E1:27"/><i><font color="Green" title="E13">A1</font></i>: 
for <font color="Olive" title="b1">w</font> being <a href="rat_1.html#V1" title="RAT_1:attr.1">rational</a>  <a href="ordinal1.html#NM1" title="ORDINAL1:NM.1">number</a>  holds  <font color="Olive" title="b1">w</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">X</font>
 ;<br/>

<b>thus </b><a NAME="E2:27"/>
<font color="Maroon" title="c1">X</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="numbers.html#K3" title="NUMBERS:func.3">RAT</a> 
 <b>by </b><i><a class="ref" href="membered.html#T4" target="_self" title="MEMBERED:th.4">Th4</a></i>; <i><font color="Red">:: according to </font></i><a class="ref" href="xboole_0.html#D10" title="XBOOLE_0:def.10">XBOOLE_0:def 10</a><br/>

<b>let </b><font color="Maroon" title="c2">e</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3" title="TARSKI:def.3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E3:27"/>
<font color="Maroon" title="c2">e</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="numbers.html#K3" title="NUMBERS:func.3">RAT</a> 
 ;<br/>

<a NAME="E4:27"/><b>then </b>
<font color="Maroon" title="c2">e</font> is <a href="rat_1.html#V1" title="RAT_1:attr.1">rational</a>
 
<b>by </b><i><a class="ref" href="rat_1.html#D2" title="RAT_1:def.2">RAT_1:def 2</a></i>;<br/>
<b>hence </b><a NAME="E5:27"/>
<font color="Maroon" title="c2">e</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">X</font>
 <b>by </b><i><a class="txt" href="membered.html#E1:27"><i><font color="Green" title="E13">A1</font></i></a></i>;<br/>


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