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<b>let </b><font color="Maroon">Z</font> be   <a href="trees_1.html#NM1">Tree</a>, <font color="Maroon">Z1</font> be   <a href="trees_1.html#NM1">Tree</a>, <font color="Maroon">Z2</font> be   <a href="trees_1.html#NM1">Tree</a>;<br/><b>let </b><font color="Maroon">z</font> be    <a href="trees_1.html#M1">Element</a> of <font color="Maroon">Z</font>;<br/>



<b>assume </b><a NAME="E1:14"/><i><font color="Green">E37</font></i>: 
<font color="Maroon">Z</font> <a href="trees_1.html#K5">with-replacement</a> <font color="Maroon">z</font>,<font color="Maroon">Z1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">Z</font> <a href="trees_1.html#K5">with-replacement</a> <font color="Maroon">z</font>,<font color="Maroon">Z2</font>
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="14_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">s</font> be    <a href="finseq_1.html#M2">FinSequence</a> of  <a href="numbers.html#K5">NAT</a> ;<br/><b>thus </b><a NAME="E1:14_1"/>
( <font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z1</font> implies <font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z2</font> )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="14_1_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:14_1_1"/><i><font color="Green">E38</font></i>: 
<font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z1</font>
 ;<br/>

<div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="14_1_1_1"><b>per </b></a><a class="txt" onclick="hs(this)" href="javascript:()"><b>cases </b></a><span class="hide"><a NAME="E1:14_1_1_1"/>
( <font color="Maroon">s</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  or <font color="Maroon">s</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 </span>;<br/><div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="14_1_1_1_1"><b>suppose </b></a><a NAME="E1:14_1_1_1_1"/>
<font color="Maroon">s</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/><div class="add"><b>hence </b><a NAME="E2:14_1_1_1_1"/>
<font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z2</font>
 <b>by </b><i><a class="ref" href="trees_1.html#T47">TREES_1:47</a></i>;<br/></div><b>end;</b></div><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="14_1_1_1_2"><b>suppose </b></a><a NAME="E1:14_1_1_1_2"/>
<font color="Maroon">s</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/><div class="add"><a NAME="E2:14_1_1_1_2"/><b>then </b><i><font color="Green">E39</font></i>: 
<font color="Maroon">z</font> <a href="trees_1.html#NR3" target="_self">is_a_proper_prefix_of</a> <font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s</font>
 <b>by </b><i><a class="ref" href="trees_1.html#T33">TREES_1:33</a></i>;<br/><a NAME="E3:14_1_1_1_2"/>
<font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z</font> <a href="trees_1.html#K5">with-replacement</a> <font color="Maroon">z</font>,<font color="Maroon">Z2</font>
 <b>by </b><i>, , <a class="ref" href="trees_1.html#D12">TREES_1:def 12</a></i>;<br/><a NAME="E4:14_1_1_1_2"/><b>then </b>
 ex <font color="Olive">w</font> being   <a href="finseq_1.html#M2">FinSequence</a> of  <a href="numbers.html#K5">NAT</a>  st <br/>( <font color="Olive">w</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z2</font> &amp; <font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s</font> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Olive">w</font> )
 <b>by </b><i>, <a class="ref" href="trees_1.html#D12">TREES_1:def 12</a></i>;<br/><b>hence </b><a NAME="E5:14_1_1_1_2"/>
<font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z2</font>
 <b>by </b><i><a class="ref" href="finseq_1.html#T46">FINSEQ_1:46</a></i>;<br/></div><b>end;</b></div></div><b>end;</b></div>

</div><b>end;</b></div><b>assume </b><a NAME="E2:14_1"/><i><font color="Green">E41</font></i>: 
<font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z2</font>
 ;<br/><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="14_1_2"><b>per </b></a><a class="txt" onclick="hs(this)" href="javascript:()"><b>cases </b></a><span class="hide"><a NAME="E1:14_1_2"/>
( <font color="Maroon">s</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  or <font color="Maroon">s</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 </span>;<br/><div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="14_1_2_1"><b>suppose </b></a><a NAME="E1:14_1_2_1"/>
<font color="Maroon">s</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/><div class="add"><b>hence </b><a NAME="E2:14_1_2_1"/>
<font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z1</font>
 <b>by </b><i><a class="ref" href="trees_1.html#T47">TREES_1:47</a></i>;<br/></div><b>end;</b></div><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="14_1_2_2"><b>suppose </b></a><a NAME="E1:14_1_2_2"/>
<font color="Maroon">s</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/><div class="add"><a NAME="E2:14_1_2_2"/><b>then </b><i><font color="Green">E44</font></i>: 
<font color="Maroon">z</font> <a href="trees_1.html#NR3" target="_self">is_a_proper_prefix_of</a> <font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s</font>
 <b>by </b><i><a class="ref" href="trees_1.html#T33">TREES_1:33</a></i>;<br/><a NAME="E3:14_1_2_2"/>
<font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z</font> <a href="trees_1.html#K5">with-replacement</a> <font color="Maroon">z</font>,<font color="Maroon">Z1</font>
 <b>by </b><i>, , <a class="ref" href="trees_1.html#D12">TREES_1:def 12</a></i>;<br/><a NAME="E4:14_1_2_2"/><b>then </b>
 ex <font color="Olive">w</font> being   <a href="finseq_1.html#M2">FinSequence</a> of  <a href="numbers.html#K5">NAT</a>  st <br/>( <font color="Olive">w</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z1</font> &amp; <font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Maroon">s</font> <a href="hidden.html#R1">=</a> <font color="Maroon">z</font> <a href="finseq_1.html#K8">^</a> <font color="Olive">w</font> )
 <b>by </b><i>, <a class="ref" href="trees_1.html#D12">TREES_1:def 12</a></i>;<br/><b>hence </b><a NAME="E5:14_1_2_2"/>
<font color="Maroon">s</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Z1</font>
 <b>by </b><i><a class="ref" href="finseq_1.html#T46">FINSEQ_1:46</a></i>;<br/></div><b>end;</b></div></div><b>end;</b></div></div><b>end;</b></div>
<b>hence </b><a NAME="E3:14"/>
<font color="Maroon">Z1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">Z2</font>
 <b>by </b><i><a class="ref" href="trees_2.html#D1">TREES_2:def 1</a></i>;<br/>


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