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<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">p1</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">p2</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">p3</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">q</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/>









<b>set </b><font color="Maroon">f</font> = <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span>;<br/>
<a NAME="E1:21"/><i><font color="Green">E28</font></i>: 
 <a href="finseq_1.html#K3">len</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="hidden.html#R1">=</a> 3
 
<b>by </b><i><a class="ref" href="finseq_1.html#T62">FINSEQ_1:62</a></i>;<br/>
<a NAME="E2:21"/><i><font color="Green">E29</font></i>: 
( 1 <a href="xxreal_0.html#R1">&lt;=</a> 3 &amp; 3 <a href="xxreal_0.html#R1">&lt;=</a>  <a href="finseq_1.html#K3">len</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> )
 
<b>by </b><i><a class="ref" href="finseq_1.html#T62">FINSEQ_1:62</a></i>;<br/>
<a NAME="E3:21"/><i><font color="Green">E30</font></i>: 
1 <a href="hidden.html#R2">in</a>  <a href="finseq_1.html#K4">dom</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span>
 
<b>by </b><i>, <a class="ref" href="finseq_3.html#T27">FINSEQ_3:27</a></i>;<br/>
<a NAME="E4:21"/><i><font color="Green">E31</font></i>: 
2 <a href="hidden.html#R2">in</a>  <a href="finseq_1.html#K4">dom</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span>
 
<b>by </b><i>, <a class="ref" href="finseq_3.html#T27">FINSEQ_3:27</a></i>;<br/>
<i><font color="Green">E33</font></i>: 3 <a href="binarith.html#K3">-'</a> 1 = 
<span class="p1">(<span class="default">2 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="binarith.html#K3">-'</a> 1

<br/>.= 
2
<b>by </b><i><a class="ref" href="binarith.html#T39">BINARITH:39</a></i>
;<br/>
 <a href="finseq_7.html#K1" target="_self">Replace</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span>,3,<font color="Maroon">q</font> = 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><span class="p3"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_1.html#K17">|</a> <span class="p3">(<span class="default">3 <a href="binarith.html#K3">-'</a> 1</span>)</span></span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p1">(<span class="default"><span class="p2"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="rfinseq.html#K1">/^</a> 3</span>)</span>
<b>by </b><i>, </i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><span class="p3"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_1.html#K17">|</a> 2</span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p1">(<span class="default"><span class="p2"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="rfinseq.html#K1">/^</a> <span class="p2">(<span class="default"><a href="finseq_1.html#K3">len</a> <span class="p3"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span></span>)</span></span>)</span>
<b>by </b><i>, <a class="ref" href="finseq_1.html#T62">FINSEQ_1:62</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><span class="p3"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_1.html#K17">|</a> 2</span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K7">^</a> <a href="xboole_0.html#K1">{}</a> 
<b>by </b><i><a class="ref" href="revrot_1.html#T2">REVROT_1:2</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_1.html#K17">|</a> 2</span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i><a class="ref" href="finseq_1.html#T47">FINSEQ_1:47</a></i>
<br/>.= 
<span class="p1"><a href="finseq_4.html#K2">&lt;*</a><span class="default"><span class="p2">(<span class="default"><span class="p3"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_4.html#K4">/.</a> 1</span>)</span>,<span class="p2">(<span class="default"><span class="p3"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_4.html#K4">/.</a> 2</span>)</span></span><a href="finseq_4.html#K2">*&gt;</a></span> <a href="finseq_1.html#K8">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i>, <a class="ref" href="jordan8.html#T1">JORDAN8:1</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_4.html#K4">/.</a> 1</span>)</span></span><a href="finseq_1.html#K12">*&gt;</a></span> <a href="finseq_1.html#K8">^</a> <span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_4.html#K4">/.</a> 2</span>)</span></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i><a class="ref" href="finseq_1.html#D9">FINSEQ_1:def 9</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="funct_1.html#K1">.</a> 1</span>)</span></span><a href="finseq_1.html#K9">*&gt;</a></span> <a href="finseq_1.html#K7">^</a> <span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="finseq_4.html#K4">/.</a> 2</span>)</span></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K7">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i>, <a class="ref" href="finseq_4.html#D4">FINSEQ_4:def 4</a></i>
<br/>.= 
<span class="p1">(<span class="default"><span class="p2"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="funct_1.html#K1">.</a> 1</span>)</span></span><a href="finseq_1.html#K9">*&gt;</a></span> <a href="finseq_1.html#K7">^</a> <span class="p2"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="funct_1.html#K1">.</a> 2</span>)</span></span><a href="finseq_1.html#K9">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K7">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i>, <a class="ref" href="finseq_4.html#D4">FINSEQ_4:def 4</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">p1</font></span><a href="finseq_1.html#K12">*&gt;</a></span> <a href="finseq_1.html#K7">^</a> <span class="p2"><a href="finseq_1.html#K9">&lt;*</a><span class="default"><span class="p3">(<span class="default"><span class="p4"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span> <a href="funct_1.html#K1">.</a> 2</span>)</span></span><a href="finseq_1.html#K9">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K7">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i><a class="ref" href="finseq_1.html#T62">FINSEQ_1:62</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">p1</font></span><a href="finseq_1.html#K12">*&gt;</a></span> <a href="finseq_1.html#K8">^</a> <span class="p2"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">p2</font></span><a href="finseq_1.html#K12">*&gt;</a></span></span>)</span> <a href="finseq_1.html#K8">^</a> <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">q</font></span><a href="finseq_1.html#K12">*&gt;</a></span>
<b>by </b><i><a class="ref" href="finseq_1.html#T62">FINSEQ_1:62</a></i>
;<br/>
<b>hence </b><a NAME="E7:21"/>
 <a href="finseq_7.html#K1" target="_self">Replace</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font></span><a href="finseq_4.html#K3">*&gt;</a></span>,3,<font color="Maroon">q</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="finseq_4.html#K3">&lt;*</a><span class="default"><font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">q</font></span><a href="finseq_4.html#K3">*&gt;</a></span>
 <b>by </b><i><a class="ref" href="finseq_1.html#D10">FINSEQ_1:def 10</a></i>;<br/>


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