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<b>let </b><font color="Maroon">S</font> be   <a href="analoaf.html#NM1">OAffinSpace</a>;<br/><b>let </b><font color="Maroon">x</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">S</font>;<br/><b>let </b><font color="Maroon">y</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">S</font>;<br/><b>let </b><font color="Maroon">z</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">S</font>;<br/><b>let </b><font color="Maroon">t</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">S</font>;<br/>









<b>assume </b><a NAME="E1:29"/>
<font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">z</font>,<font color="Maroon">t</font>
 ;<br/>

<a NAME="E2:29"/><b>then </b><i><font color="Green">E21</font></i>: 
( <font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">z</font>,<font color="Maroon">t</font> or <font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">t</font>,<font color="Maroon">z</font> )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:29"/>
<font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">t</font>,<font color="Maroon">z</font>
 <b>by </b><i/>;<br/>

<a NAME="E4:29"/>
( <font color="Maroon">y</font>,<font color="Maroon">x</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">t</font>,<font color="Maroon">z</font> or <font color="Maroon">y</font>,<font color="Maroon">x</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">z</font>,<font color="Maroon">t</font> )
 
<b>by </b><i>, <a class="ref" href="analoaf.html#D5">ANALOAF:def 5</a></i>;<br/>
<b>hence </b><a NAME="E5:29"/>
( <font color="Maroon">y</font>,<font color="Maroon">x</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">z</font>,<font color="Maroon">t</font> &amp; <font color="Maroon">y</font>,<font color="Maroon">x</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">t</font>,<font color="Maroon">z</font> )
 <b>by </b><i/>;<br/>

<a NAME="E6:29"/>
( <font color="Maroon">z</font>,<font color="Maroon">t</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> or <font color="Maroon">z</font>,<font color="Maroon">t</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">y</font>,<font color="Maroon">x</font> )
 
<b>by </b><i>, </i>;<br/>
<b>hence </b><a NAME="E7:29"/>
( <font color="Maroon">z</font>,<font color="Maroon">t</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> &amp; <font color="Maroon">z</font>,<font color="Maroon">t</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">y</font>,<font color="Maroon">x</font> )
 <b>by </b><i/>;<br/>

<a NAME="E8:29"/>
( <font color="Maroon">t</font>,<font color="Maroon">z</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">y</font>,<font color="Maroon">x</font> or <font color="Maroon">t</font>,<font color="Maroon">z</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> )
 
<b>by </b><i>, </i>;<br/>
<b>hence </b><a NAME="E9:29"/>
( <font color="Maroon">t</font>,<font color="Maroon">z</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> &amp; <font color="Maroon">t</font>,<font color="Maroon">z</font> <a href="diraf.html#R2" target="_self">'||'</a> <font color="Maroon">y</font>,<font color="Maroon">x</font> )
 <b>by </b><i/>;<br/>


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