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<b>let </b><font color="Maroon">D</font> be  non <a href="xboole_0.html#V1">empty</a> <a href="finset_1.html#V1">finite</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">A</font> be  <a href="rearran1.html#V3" target="_self">lenght_equal_card_of_set</a>  <a href="finseq_1.html#M2">FinSequence</a> of  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">D</font>;<br/>



<b>assume </b><a NAME="E1:13"/>
 <a href="finseq_1.html#K3">len</a> <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> 0
 ;<br/>

<a NAME="E2:13"/><b>then </b>
 <a href="card_1.html#K4">card</a> <font color="Maroon">D</font> <a href="hidden.html#R1">=</a> 0
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:13"/>
contradiction
 <b>by </b><i><a class="ref" href="card_2.html#T59">CARD_2:59</a></i>;<br/>


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