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<b>let </b><font color="Maroon">W</font> be   <a href="classes2.html#NM1">Universe</a>;<br/><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/>



<a NAME="E1:10"/>
( ( <font color="Maroon">x</font> is    <a href="ordinal4.html#M1">Ordinal</a> of <font color="Maroon">W</font> implies ( <font color="Maroon">x</font> is   <a href="ordinal1.html#NM2">Ordinal</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">W</font> ) ) &amp; ( <font color="Maroon">x</font> is   <a href="ordinal1.html#NM2">Ordinal</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">W</font> implies <font color="Maroon">x</font> is    <a href="ordinal4.html#M1">Ordinal</a> of <font color="Maroon">W</font> ) &amp; ( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="ordinal1.html#K3">On</a> <font color="Maroon">W</font> implies ( <font color="Maroon">x</font> is   <a href="ordinal1.html#NM2">Ordinal</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">W</font> ) ) &amp; ( <font color="Maroon">x</font> is   <a href="ordinal1.html#NM2">Ordinal</a> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">W</font> implies <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="ordinal1.html#K3">On</a> <font color="Maroon">W</font> ) )
 
<b>by </b><i><a class="ref" href="ordinal1.html#D10">ORDINAL1:def 10</a>, <a class="ref" href="ordinal4.html#D2">ORDINAL4:def 2</a></i>;<br/>
<b>hence </b><a NAME="E2:10"/>
( <font color="Maroon">x</font> is    <a href="ordinal4.html#M1">Ordinal</a> of <font color="Maroon">W</font> iff <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="ordinal1.html#K3">On</a> <font color="Maroon">W</font> )
 ;<br/>


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