<?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/>

<a NAME="E1:84"/>
for <font color="Olive">b<sub>1</sub></font> being   <a href="hidden.html#M1">set</a>  holds <br/>( <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R2">in</a>  <a href="partfun1.html#K4" target="_self">PFuncs</a> <font color="Maroon">c<sub>1</sub></font>,<a href="xboole_0.html#K1">{}</a>  iff <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  )
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="84_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">c<sub>2</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>thus </b><a NAME="E1:84_1"/>
( <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R2">in</a>  <a href="partfun1.html#K4" target="_self">PFuncs</a> <font color="Maroon">c<sub>1</sub></font>,<a href="xboole_0.html#K1">{}</a>  implies <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="84_1_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:84_1_1"/>
<font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R2">in</a>  <a href="partfun1.html#K4" target="_self">PFuncs</a> <font color="Maroon">c<sub>1</sub></font>,<a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<a NAME="E2:84_1_1"/><b>then </b>
<font color="Maroon">c<sub>2</sub></font> is   <a href="partfun1.html#NM1">PartFunc</a> of <font color="Maroon">c<sub>1</sub></font>, <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="partfun1.html#T120" target="_self">Th120</a></i>;<br/>
<b>hence </b><a NAME="E3:84_1_1"/>
<font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 <b>by </b><i><a class="ref" href="partfun1.html#T64" target="_self">Th64</a></i>;<br/>


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

<a NAME="E2:84_1"/>
 <a href="xboole_0.html#K1">{}</a>  is   <a href="partfun1.html#NM1">PartFunc</a> of <font color="Maroon">c<sub>1</sub></font>, <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="txt" href="partfun1.html#E4"><i><font color="Green">Lemma4</font></i></a>, <a class="ref" href="partfun1.html#T55" target="_self">Th55</a></i>;<br/>
<b>hence </b><a NAME="E3:84_1"/>
( <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  implies <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R2">in</a>  <a href="partfun1.html#K4" target="_self">PFuncs</a> <font color="Maroon">c<sub>1</sub></font>,<a href="xboole_0.html#K1">{}</a>  )
 <b>by </b><i><a class="ref" href="partfun1.html#T119" target="_self">Th119</a></i>;<br/>


</div><b>end;</b></div>
<b>hence </b><a NAME="E2:84"/>
 <a href="partfun1.html#K4" target="_self">PFuncs</a> <font color="Maroon">c<sub>1</sub></font>,<a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><a href="xboole_0.html#K1">{}</a> </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/>


</div>
