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<b>let </b><font color="Maroon">a</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">b</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">D</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">f</font> be    <a href="finseq_1.html#M2">FinSequence</a> of <font color="Maroon">D</font>;<br/>









<b>assume </b><a NAME="E1:16"/><i><font color="Green">E33</font></i>: 
<font color="Maroon">f</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="finseq_1.html#K11">&lt;*</a><span class="default"><font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font></span><a href="finseq_1.html#K11">*&gt;</a></span>
 ;<br/>

<b>then reconsider </b><font color="Maroon">a2</font> = <font color="Maroon">a</font>, <font color="Maroon">b2</font> = <font color="Maroon">b</font>, <font color="Maroon">c2</font> = <font color="Maroon">c</font> as    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font> <b>by </b><i/>;<br/>
<font color="Maroon">f</font> <a href="rfinseq.html#K1">/^</a> 2 = 
<span class="p1">(<span class="default"><span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">a2</font></span><a href="finseq_1.html#K12">*&gt;</a></span> <a href="finseq_8.html#K1">^</a> <span class="p2"><a href="finseq_4.html#K2">&lt;*</a><span class="default"><font color="Maroon">b2</font>,<font color="Maroon">c2</font></span><a href="finseq_4.html#K2">*&gt;</a></span></span>)</span> <a href="rfinseq.html#K1">/^</a> <span class="p1">(<span class="default">1 <a href="nat_1.html#K1">+</a> 1</span>)</span>
<b>by </b><i>, <a class="ref" href="finseq_1.html#T60">FINSEQ_1:60</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">a2</font></span><a href="finseq_1.html#K12">*&gt;</a></span> <a href="finseq_8.html#K1">^</a> <span class="p2"><a href="finseq_4.html#K2">&lt;*</a><span class="default"><font color="Maroon">b2</font>,<font color="Maroon">c2</font></span><a href="finseq_4.html#K2">*&gt;</a></span></span>)</span> <a href="rfinseq.html#K1">/^</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p3"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">a2</font></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="nat_1.html#K1">+</a> 1</span>)</span>
<b>by </b><i><a class="ref" href="finseq_1.html#T57">FINSEQ_1:57</a></i>
<br/>.= 
<span class="p1"><a href="finseq_4.html#K2">&lt;*</a><span class="default"><font color="Maroon">b2</font>,<font color="Maroon">c2</font></span><a href="finseq_4.html#K2">*&gt;</a></span> <a href="rfinseq.html#K1">/^</a> 1
<b>by </b><i><a class="ref" href="finseq_5.html#T39">FINSEQ_5:39</a></i>
<br/>.= 
<span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">c2</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i><a class="ref" href="finseq_6.html#T50">FINSEQ_6:50</a></i>
;<br/>
<b>hence </b><a NAME="E4:16"/>
<font color="Maroon">f</font> <a href="rfinseq.html#K1">/^</a> 2 <a href="hidden.html#R1">=</a> <span class="p1"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><font color="Maroon">c</font></span><a href="finseq_1.html#K9">*&gt;</a></span>
 ;<br/>


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