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<b>let </b><font color="Maroon">a</font> be    <a href="subset_1.html#M2">Element</a> of  <a href="numbers.html#K5">NAT</a> ;<br/><b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/>



<b>assume </b><a NAME="E1:36"/><i><font color="Green">E40</font></i>: 
0 <a href="hidden.html#R2">in</a> <font color="Maroon">X</font>
 ;<br/>

<b>let </b><font color="Maroon">s</font> be    <a href="finseq_1.html#M2">FinSequence</a> of <font color="Maroon">X</font>;<br/>

<a NAME="E2:36"/><i><font color="Green">E41</font></i>: 
( <font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">a</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K2">rng</a> <font color="Maroon">s</font> or <font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">a</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  )
 
<b>by </b><i/>;<br/>
<a NAME="E3:36"/>
 <a href="relat_1.html#K2">rng</a> <font color="Maroon">s</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">X</font>
 
<b>by </b><i><a class="ref" href="finseq_1.html#D4">FINSEQ_1:def 4</a></i>;<br/>
<b>hence </b><a NAME="E4:36"/>
<font color="Maroon">s</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">a</font> is    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">X</font>
 <b>by </b><i>, </i>;<br/>


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