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<b>let </b><font color="Maroon">C</font> be   <a href="ordinal1.html#NM2">Ordinal</a>;<br/><b>let </b><font color="Maroon">A</font> be   <a href="ordinal1.html#NM2">Ordinal</a>;<br/>



<b>assume </b><a NAME="E1:36"/><i><font color="Green">E13</font></i>: 
( 1 <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> &amp; <font color="Maroon">A</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 ;<br/>

<a NAME="E2:36"/><b>then </b>
(  <a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> &amp;  <a href="ordinal2.html#K12">exp</a> <font color="Maroon">C</font>,<a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R1">=</a> 1 )
 
<b>by </b><i><a class="ref" href="ordinal2.html#T60">ORDINAL2:60</a>, <a class="ref" href="ordinal3.html#T10">ORDINAL3:10</a></i>;<br/>
<b>hence </b><a NAME="E3:36"/>
1 <a href="hidden.html#R2">in</a>  <a href="ordinal2.html#K12">exp</a> <font color="Maroon">C</font>,<font color="Maroon">A</font>
 <b>by </b><i>, </i>;<br/>


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