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

<b>let </b><font color="Maroon" title="c1">PS</font> be   <a href="parsp_1.html#NM2" title="PARSP_1:NM.2">ParSp</a>;<br/><b>let </b><font color="Maroon" title="c2">p</font>, <font color="Maroon" title="c3">q</font>, <font color="Maroon" title="c4">r</font>, <font color="Maroon" title="c5">s</font> be   <a href="struct_0.html#NM1" title="STRUCT_0:NM.1">Element</a> of <font color="Maroon" title="c1">PS</font>;<br/>









<b>assume </b><a NAME="E1:56"/>
( not <font color="Maroon" title="c2">p</font>,<font color="Maroon" title="c3">q</font> <a href="parsp_1.html#R1" title="PARSP_1:pred.1">'||'</a> <font color="Maroon" title="c2">p</font>,<font color="Maroon" title="c4">r</font> &amp; <font color="Maroon" title="c2">p</font>,<font color="Maroon" title="c4">r</font> <a href="parsp_1.html#R1" title="PARSP_1:pred.1">'||'</a> <font color="Maroon" title="c2">p</font>,<font color="Maroon" title="c5">s</font> &amp; <font color="Maroon" title="c3">q</font>,<font color="Maroon" title="c4">r</font> <a href="parsp_1.html#R1" title="PARSP_1:pred.1">'||'</a> <font color="Maroon" title="c3">q</font>,<font color="Maroon" title="c5">s</font> )
 ;<br/>

<a NAME="E2:56"/><b>then </b>
( not <font color="Maroon" title="c4">r</font>,<font color="Maroon" title="c2">p</font> <a href="parsp_1.html#R1" title="PARSP_1:pred.1">'||'</a> <font color="Maroon" title="c4">r</font>,<font color="Maroon" title="c3">q</font> &amp; <font color="Maroon" title="c4">r</font>,<font color="Maroon" title="c5">s</font> <a href="parsp_1.html#R1" title="PARSP_1:pred.1">'||'</a> <font color="Maroon" title="c4">r</font>,<font color="Maroon" title="c2">p</font> &amp; <font color="Maroon" title="c4">r</font>,<font color="Maroon" title="c5">s</font> <a href="parsp_1.html#R1" title="PARSP_1:pred.1">'||'</a> <font color="Maroon" title="c4">r</font>,<font color="Maroon" title="c3">q</font> )
 
<b>by </b><i><a class="ref" href="parsp_1.html#T47" target="_self" title="PARSP_1:th.47">Th47</a></i>;<br/>
<b>hence </b><a NAME="E3:56"/>
<font color="Maroon" title="c4">r</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c5">s</font>
 <b>by </b><i><a class="ref" href="parsp_1.html#D12" target="_self" title="PARSP_1:def.12">Def12</a></i>;<br/>


</div>
