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



<b>assume </b><b>that </b><br/><a NAME="E1:18_2_2"/><i><font color="Green">E25</font></i>: 
(  <a href="ordinal1.html#K3">On</a> <font color="Maroon">X</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">B</font> &amp; ( for <font color="Olive">A</font> being  <a href="ordinal1.html#NM2">Ordinal</a>  st  <a href="ordinal1.html#K3">On</a> <font color="Maroon">X</font> <a href="tarski.html#R1">c=</a> <font color="Olive">A</font> holds <br/><font color="Maroon">B</font> <a href="ordinal1.html#R1">c=</a> <font color="Olive">A</font> ) )
 <b>and </b><br/><a NAME="E2:18_2_2"/><i><font color="Green">E26</font></i>: 
(  <a href="ordinal1.html#K3">On</a> <font color="Maroon">X</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">C</font> &amp; ( for <font color="Olive">A</font> being  <a href="ordinal1.html#NM2">Ordinal</a>  st  <a href="ordinal1.html#K3">On</a> <font color="Maroon">X</font> <a href="tarski.html#R1">c=</a> <font color="Olive">A</font> holds <br/><font color="Maroon">C</font> <a href="ordinal1.html#R1">c=</a> <font color="Olive">A</font> ) )
 ;<br/>

<b>thus </b><a NAME="E3:18_2_2"/>
( <font color="Maroon">B</font> <a href="ordinal1.html#R1">c=</a> <font color="Maroon">C</font> &amp; <font color="Maroon">C</font> <a href="ordinal1.html#R1">c=</a> <font color="Maroon">B</font> )
 <b>by </b><i>, </i>; <i><font color="Red">:: according to </font></i><a class="ref" href="xboole_0.html#D10">XBOOLE_0:def 10</a><br/>


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