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<b>let </b><font color="Maroon">G</font> be   <a href="projpl_1.html#NM1">IncProjectivePlane</a>;<br/><b>let </b><font color="Maroon">a</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>, <font color="Maroon">b</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>, <font color="Maroon">c</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>, <font color="Maroon">d</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>;<br/>



<b>assume </b><a NAME="E1:39"/><i><font color="Green">E36</font></i>: 
( <font color="Maroon">a</font> <a href="projpl_1.html#K1" target="_self">*</a> <font color="Maroon">c</font> <a href="hidden.html#R1">=</a> <font color="Maroon">b</font> <a href="projpl_1.html#K1" target="_self">*</a> <font color="Maroon">d</font> &amp; not <font color="Maroon">a</font> <a href="hidden.html#R1">=</a> <font color="Maroon">c</font> &amp; not <font color="Maroon">b</font> <a href="hidden.html#R1">=</a> <font color="Maroon">d</font> &amp; not <font color="Maroon">c</font> <a href="hidden.html#R1">=</a> <font color="Maroon">d</font> )
 ;<br/>

<a NAME="E2:39"/><b>then </b>
<font color="Maroon">a</font> <a href="projpl_1.html#K1" target="_self">*</a> <font color="Maroon">c</font> <a href="hidden.html#R1">=</a> <font color="Maroon">c</font> <a href="projpl_1.html#K1" target="_self">*</a> <font color="Maroon">d</font>
 
<b>by </b><i><a class="ref" href="projpl_1.html#T1" target="_self">Th1</a></i>;<br/>
<b>hence </b><a NAME="E3:39"/>
<font color="Maroon">a</font> <a href="incsp_1.html#R1">on</a> <font color="Maroon">c</font> <a href="projpl_1.html#K1" target="_self">*</a> <font color="Maroon">d</font>
 <b>by </b><i>, </i>;<br/>


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