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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="card_5.html#NM1">Aleph</a>;<br/>

<a NAME="E1:37"/><i><font color="Green">E26</font></i>: 
( <font color="Maroon">c<sub>1</sub></font> <a href="zfrefle1.html#R4">is_cofinal_with</a>  <a href="card_5.html#K1" target="_self">cf</a> <font color="Maroon">c<sub>1</sub></font> &amp; <font color="Maroon">c<sub>1</sub></font> <a href="ordinal1.html#NR2" target="_self">is_limit_ordinal</a>  &amp; <font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>1</sub></font> )
 
<b>by </b><i><a class="ref" href="card_5.html#D2" target="_self">Def2</a>, <a class="ref" href="card_4.html#T32">CARD_4:32</a></i>;<br/>
<a NAME="E2:37"/><b>then </b><i><font color="Green">E27</font></i>: 
 <a href="card_5.html#K1" target="_self">cf</a> <font color="Maroon">c<sub>1</sub></font> <a href="ordinal1.html#NR2" target="_self">is_limit_ordinal</a> 
 
<b>by </b><i><a class="ref" href="zfrefle1.html#T27">ZFREFLE1:27</a></i>;<br/>
<a NAME="E3:37"/>
 <a href="card_5.html#K1" target="_self">cf</a> <font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="txt" href="card_5.html#E1:37"><i><font color="Green">E26</font></i></a>, <a class="ref" href="zfrefle1.html#T28">ZFREFLE1:28</a></i>;<br/>
<a NAME="E4:37"/><b>then </b>
 <a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R2">in</a>  <a href="card_5.html#K1" target="_self">cf</a> <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="ref" href="ordinal3.html#T10">ORDINAL3:10</a></i>;<br/>
<b>hence </b><a NAME="E5:37"/>
 <a href="card_1.html#K3">alef</a> 0 <a href="card_1.html#NR1" target="_self">&lt;=`</a>  <a href="card_5.html#K1" target="_self">cf</a> <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="txt" href="card_5.html#E2:37"><i><font color="Green">E27</font></i></a>, <a class="ref" href="card_1.html#T83">CARD_1:83</a>, <a class="ref" href="ordinal1.html#D12">ORDINAL1:def 12</a></i>;<br/>


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