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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>assume </b><a NAME="E1:5_1_1"/>
<font color="Maroon">c<sub>1</sub></font> is <a href="ordinal1.html#V7">natural</a>
 ;<br/>

<a NAME="E2:5_1_1"/><b>then </b>
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R2">in</a>  <a href="ordinal1.html#K5">omega</a> 
 
<b>by </b><i><a class="ref" href="ordinal1.html#D13">ORDINAL1:def 13</a></i>;<br/>
<b>hence </b><a NAME="E3:5_1_1"/>
<font color="Maroon">c<sub>1</sub></font> is <a href="card_1.html#V1">cardinal</a>
 <b>by </b><i><a class="ref" href="card_1.html#T65">CARD_1:65</a></i>;<br/>


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