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<b>let </b><font color="Maroon">A</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/>

<a NAME="E1:65"/><i><font color="Green">E43</font></i>: 
 <a href="relat_1.html#K1">dom</a> <span class="p1"><a href="monoid_1.html#K20" target="_self">|.</a><span class="default"><span class="p2">(<span class="default"><a href="finseq_1.html#K6">&lt;*&gt;</a> <font color="Maroon">A</font></span>)</span></span><a href="monoid_1.html#K20" target="_self">.|</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">A</font>
 
<b>by </b><i/>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="65_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>assume </b><a NAME="E1:65_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font>
 ;<br/><b>then reconsider </b><font color="Maroon">a</font> = <font color="Maroon">x</font> as    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font> ;<br/><b>thus </b><span class="p1"><a href="monoid_1.html#K20" target="_self">|.</a><span class="default"><span class="p2">(<span class="default"><a href="finseq_1.html#K6">&lt;*&gt;</a> <font color="Maroon">A</font></span>)</span></span><a href="monoid_1.html#K20" target="_self">.|</a></span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> = 
 <a href="card_1.html#K4">card</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1">dom</a> <span class="p2">(<span class="default"><span class="p3"><a href="domain_1.html#K6">{</a><span class="default"><font color="Maroon">a</font></span><a href="domain_1.html#K6">}</a></span> <a href="relat_1.html#K8">|</a> <a href="xboole_0.html#K1">{}</a> </span>)</span></span>)</span>
<b>by </b><i/>
<br/>.= 
0
<b>by </b><i><a class="ref" href="card_1.html#T78">CARD_1:78</a>, <a class="ref" href="relat_1.html#T60">RELAT_1:60</a>, <a class="ref" href="relat_1.html#T138">RELAT_1:138</a></i>
;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E3:65"/>
<span class="p1"><a href="monoid_1.html#K20" target="_self">|.</a><span class="default"><span class="p2">(<span class="default"><a href="finseq_1.html#K6">&lt;*&gt;</a> <font color="Maroon">A</font></span>)</span></span><a href="monoid_1.html#K20" target="_self">.|</a></span> <a href="hidden.html#R1">=</a> <font color="Maroon">A</font> <a href="monoid_1.html#K17" target="_self">--&gt;</a> 0
 <b>by </b><i><a class="ref" href="monoid_1.html#T1" target="_self">Th1</a>, <a class="ref" href="funcop_1.html#T17">FUNCOP_1:17</a></i>;<br/>


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