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

<b>assume </b><a NAME="E1:9_2_1"/>
<font color="Maroon">n</font> is <a href="ordinal1.html#V7">natural</a>
 ;<br/>

<a NAME="E2:9_2_1"/><b>then </b>
<font color="Maroon">n</font> is    <a href="subset_1.html#M2">Element</a> of  <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="E3:9_2_1"/>
<font color="Maroon">n</font> is <a href="int_1.html#V1" target="_self">integer</a>
 <b>by </b><i/>;<br/>


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