<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>thus </b><a NAME="E1:19"/>
( <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">c<sub>1</sub></font></span><a href="tarski.html#K1">}</a></span> is <a href="trees_3.html#V1" target="_self">constituted-Trees</a> implies <font color="Maroon">c<sub>1</sub></font> is   <a href="trees_1.html#NM1">Tree</a> )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="19_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:19_1"/><i><font color="Green">E12</font></i>: 
for <font color="Olive">b<sub>1</sub></font> being   <a href="hidden.html#M1">set</a>  st <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">c<sub>1</sub></font></span><a href="tarski.html#K1">}</a></span> holds <br/><font color="Olive">b<sub>1</sub></font> is   <a href="trees_1.html#NM1">Tree</a>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="trees_3.html#D3" target="_self">TREES_3:def 3</a><br/>

<a NAME="E2:19_1"/>
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">c<sub>1</sub></font></span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<b>hence </b><a NAME="E3:19_1"/>
<font color="Maroon">c<sub>1</sub></font> is   <a href="trees_1.html#NM1">Tree</a>
 <b>by </b><i><a class="txt" href="trees_3.html#E1:19_1"><i><font color="Green">E12</font></i></a></i>;<br/>


</div><b>end;</b></div>

<b>assume </b><a NAME="E2:19"/><i><font color="Green">E12</font></i>: 
<font color="Maroon">c<sub>1</sub></font> is   <a href="trees_1.html#NM1">Tree</a>
 ;<br/>

<b>let </b><font color="Maroon">c<sub>2</sub></font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="trees_3.html#D3" target="_self">TREES_3:def 3</a><br/>

<b>thus </b><a NAME="E3:19"/>
( <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">c<sub>1</sub></font></span><a href="tarski.html#K1">}</a></span> implies <font color="Maroon">c<sub>2</sub></font> is   <a href="trees_1.html#NM1">Tree</a> )
 <b>by </b><i><a class="txt" href="trees_3.html#E2:19"><i><font color="Green">E12</font></i></a>, <a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>


</div>
