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<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y</font> be    <a href="hidden.html#M1">set</a> ;<br/>



<b>assume </b><a NAME="E1:80"/>
( <font color="Maroon">X</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">X</font> is <a href="finset_1.html#V1">finite</a> &amp; not <font color="Maroon">Y</font> is <a href="finset_1.html#V1">finite</a> )
 ;<br/>

<a NAME="E2:80"/><b>then </b><i><font color="Green">E44</font></i>: 
(  <a href="card_1.html#K1">Card</a> <font color="Maroon">X</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> 0 &amp;  <a href="card_1.html#K1">Card</a> <font color="Maroon">X</font> is <a href="finset_1.html#V1">finite</a> &amp; not  <a href="card_1.html#K1">Card</a> <font color="Maroon">Y</font> is <a href="finset_1.html#V1">finite</a> )
 
<b>by </b><i>, <a class="ref" href="card_2.html#T59">CARD_2:59</a></i>;<br/>
<a NAME="E3:80"/><b>then </b>
(  <a href="card_1.html#K1">Card</a> <font color="Maroon">X</font> <a href="card_1.html#NR2" target="_self">&lt;`</a>  <a href="card_1.html#K1">Card</a> <font color="Maroon">Y</font> &amp; 0 <a href="card_1.html#NR2" target="_self">&lt;`</a>  <a href="card_1.html#K1">Card</a> <font color="Maroon">X</font> )
 
<b>by </b><i>, <a class="ref" href="ordinal3.html#T10">ORDINAL3:10</a></i>;<br/>
<b>hence </b><a NAME="E4:80"/>
<span class="p1">(<span class="default"><a href="card_1.html#K1">Card</a> <font color="Maroon">Y</font></span>)</span> <a href="card_2.html#K2">*`</a> <span class="p1">(<span class="default"><a href="card_1.html#K1">Card</a> <font color="Maroon">X</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="card_1.html#K1">Card</a> <font color="Maroon">Y</font>
 <b>by </b><i>, </i>;<br/>


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