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<b>let </b><font color="Maroon">OAS</font> be   <a href="analoaf.html#NM1">OAffinSpace</a>;<br/><b>let </b><font color="Maroon">a</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">OAS</font>;<br/><b>let </b><font color="Maroon">b</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">OAS</font>;<br/><b>let </b><font color="Maroon">c</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">OAS</font>;<br/><b>let </b><font color="Maroon">d</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">OAS</font>;<br/>









<b>assume </b><a NAME="E1:37"/><i><font color="Green">E29</font></i>: 
( <font color="Maroon">a</font>,<font color="Maroon">b</font> <a href="diraf.html#R2">'||'</a> <font color="Maroon">c</font>,<font color="Maroon">d</font> &amp; <font color="Maroon">a</font>,<font color="Maroon">c</font> <a href="diraf.html#R2">'||'</a> <font color="Maroon">b</font>,<font color="Maroon">d</font> &amp; not  <a href="diraf.html#R3">LIN</a> <font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font> )
 ;<br/>

<a NAME="E2:37"/><b>then </b>
( <font color="Maroon">a</font>,<font color="Maroon">b</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">c</font>,<font color="Maroon">d</font> &amp; <font color="Maroon">a</font>,<font color="Maroon">c</font> <a href="analoaf.html#R2">//</a> <font color="Maroon">b</font>,<font color="Maroon">d</font> )
 
<b>by </b><i/>;<br/>
<b>then consider </b><font color="Maroon">x</font> being   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">OAS</font><b> such that </b><br/><a NAME="E4:37"/><i><font color="Green">E30</font></i>: 
(  <a href="diraf.html#R1">Mid</a> <font color="Maroon">a</font>,<font color="Maroon">x</font>,<font color="Maroon">d</font> &amp;  <a href="diraf.html#R1">Mid</a> <font color="Maroon">b</font>,<font color="Maroon">x</font>,<font color="Maroon">c</font> )
 <b>by </b><i>, </i>;<br/>
<a NAME="E5:37"/>
(  <a href="diraf.html#R3">LIN</a> <font color="Maroon">a</font>,<font color="Maroon">x</font>,<font color="Maroon">d</font> &amp;  <a href="diraf.html#R3">LIN</a> <font color="Maroon">b</font>,<font color="Maroon">x</font>,<font color="Maroon">c</font> )
 
<b>by </b><i>, <a class="ref" href="diraf.html#T34">DIRAF:34</a></i>;<br/>
<a NAME="E6:37"/><b>then </b>
(  <a href="diraf.html#R3">LIN</a> <font color="Maroon">x</font>,<font color="Maroon">a</font>,<font color="Maroon">d</font> &amp;  <a href="diraf.html#R3">LIN</a> <font color="Maroon">x</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font> )
 
<b>by </b><i><a class="ref" href="diraf.html#T36">DIRAF:36</a></i>;<br/>
<b>hence </b><a NAME="E7:37"/>
 ex <font color="Olive">x</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">OAS</font> st <br/>(  <a href="diraf.html#R3">LIN</a> <font color="Olive">x</font>,<font color="Maroon">a</font>,<font color="Maroon">d</font> &amp;  <a href="diraf.html#R3">LIN</a> <font color="Olive">x</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font> )
 ;<br/>


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