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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="ordinal1.html#NM1" target="_self">number</a> ;<br/>

<b>assume </b><a NAME="E1:3_1_1"/>
<font color="Maroon">c<sub>1</sub></font> is <a href="ordinal1.html#V7">natural</a>
 ;<br/>

<a NAME="E2:3_1_1"/><b>then </b>
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R2">in</a>  <a href="numbers.html#K5">NAT</a> 
 
<b>by </b><i><a class="ref" href="ordinal1.html#D13">ORDINAL1:def 13</a></i>;<br/>
<b>hence </b><a NAME="E3:3_1_1"/>
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R2">in</a>  <a href="numbers.html#K1">REAL</a> 
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="xreal_0.html#D1" target="_self">XREAL_0:def 1</a><br/>


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