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<b>take </b><font color="Maroon">X</font> = <span class="p1"><a href="seq_4.html#K1">{</a><span class="default">1</span><a href="seq_4.html#K1">}</a></span>;<br/>

<b>thus </b><a NAME="E1:17_1_1"/>
( <font color="Maroon">X</font> is <a href="finset_1.html#V1">finite</a> &amp; not <font color="Maroon">X</font> is <a href="xboole_0.html#V1">empty</a> )
 ;<br/>

<b>thus </b><a NAME="E2:17_1_1"/>
<font color="Maroon">X</font> is <a href="membered.html#V5">natural-membered</a>
 ;<br/>

<b>thus </b><a NAME="E3:17_1_1"/>
<font color="Maroon">X</font> is <a href="setfam_1.html#V1">with_non-empty_elements</a>
 ;<br/>


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