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<b>let </b><font color="Maroon" title="c1">x</font>, <font color="Maroon" title="c2">y</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/><b>let </b><font color="Maroon" title="c3">p</font> be   <a href="finseq_1.html#NM1" title="FINSEQ_1:NM.1">FinSequence</a>;<br/>





<b>assume </b><a NAME="E1:27"/><i><font color="Green" title="E15">A1</font></i>: 
 <a href="trees_4.html#K1" title="TREES_4:func.1">root-tree</a> <font color="Maroon" title="c1">x</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c2">y</font> <a href="trees_4.html#K3" title="TREES_4:func.3">-flat_tree</a> <font color="Maroon" title="c3">p</font>
 ;<br/>

<b>thus </b><font color="Maroon" title="c1">x</font> = 
<span class="p1">(<span class="default"><a href="trees_4.html#K1" title="TREES_4:func.1">root-tree</a> <font color="Maroon" title="c1">x</font></span>)</span> <a href="funct_1.html#K1" title="FUNCT_1:func.1">.</a> <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
<b>by </b><i><a class="ref" href="trees_4.html#T3" target="_self" title="TREES_4:th.3">Th3</a></i>
<br/>.= 
<font color="Maroon" title="c2">y</font>
<b>by </b><i><a class="txt" href="trees_4.html#E1:27"><i><font color="Green" title="E15">A1</font></i></a>, <a class="ref" href="trees_4.html#D3" target="_self" title="TREES_4:def.3">Def3</a></i>
;<br/>

<a NAME="E3:27"/>
(  <a href="relat_1.html#K1" title="RELAT_1:func.1">dom</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">y</font> <a href="trees_4.html#K3" title="TREES_4:func.3">-flat_tree</a> <font color="Maroon" title="c3">p</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="trees_1.html#K2" title="TREES_1:func.2">elementary_tree</a> <span class="p1">(<span class="default"><a href="finseq_1.html#K3" title="FINSEQ_1:func.3">len</a> <font color="Maroon" title="c3">p</font></span>)</span> &amp;  <a href="relat_1.html#K1" title="RELAT_1:func.1">dom</a> <span class="p1">(<span class="default"><a href="trees_4.html#K1" title="TREES_4:func.1">root-tree</a> <font color="Maroon" title="c1">x</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="trees_1.html#K2" title="TREES_1:func.2">elementary_tree</a> <a href="numbers.html#K6" title="NUMBERS:func.6">0</a>  )
 
<b>by </b><i><a class="ref" href="trees_4.html#D3" target="_self" title="TREES_4:def.3">Def3</a>, <a class="ref" href="trees_4.html#T3" target="_self" title="TREES_4:th.3">Th3</a></i>;<br/>
<a NAME="E4:27"/><b>then </b>
 <a href="finseq_1.html#K3" title="FINSEQ_1:func.3">len</a> <font color="Maroon" title="c3">p</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="numbers.html#K6" title="NUMBERS:func.6">0</a> 
 
<b>by </b><i><a class="txt" href="trees_4.html#E1:27"><i><font color="Green" title="E15">A1</font></i></a>, <a class="ref" href="trees_4.html#T2" target="_self" title="TREES_4:th.2">Th2</a></i>;<br/>
<b>hence </b><a NAME="E5:27"/>
<font color="Maroon" title="c3">p</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 <b>by </b><i><a class="ref" href="finseq_1.html#T25" title="FINSEQ_1:th.25">FINSEQ_1:25</a></i>;<br/>


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