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



<b>assume </b><a NAME="E1:64"/>
( not <font color="Maroon">A</font> <a href="xboole_0.html#R2">c&lt;</a> <font color="Maroon">B</font> &amp; not <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">B</font> &amp; not <font color="Maroon">B</font> <a href="xboole_0.html#R2">c&lt;</a> <font color="Maroon">A</font> )
 ;<br/>

<a NAME="E2:64"/><b>then </b>
( not <font color="Maroon">A</font> <a href="ordinal1.html#R1" target="_self">c=</a> <font color="Maroon">B</font> &amp; not <font color="Maroon">B</font> <a href="ordinal1.html#R1" target="_self">c=</a> <font color="Maroon">A</font> )
 
<b>by </b><i><a class="ref" href="xboole_0.html#D8">XBOOLE_0:def 8</a></i>;<br/>
<b>hence </b><a NAME="E3:64"/>
contradiction
 ;<br/>


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