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<b>let </b><font color="Maroon" title="c1">G</font> be    <a href="incsp_1.html#L1" title="INCSP_1:struct.1">IncProjStr</a> ;<br/>

<b>assume </b><a NAME="E1:22"/><i><font color="Green" title="E20">A1</font></i>: 
<font color="Maroon" title="c1">G</font> is   <a href="incproj.html#NM2" title="INCPROJ:NM.2">IncProjSp</a>
 ;<br/>

<b>then consider </b><font color="Maroon" title="c2">A</font>, <font color="Maroon" title="c3">B</font> being   <a href="incsp_1.html#NM2" title="INCSP_1:NM.2">LINE</a> of <font color="Maroon" title="c1">G</font><b> such that </b><br/><a NAME="E3:22"/><i><font color="Green" title="E21">A2</font></i>: 
<font color="Maroon" title="c2">A</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a> <font color="Maroon" title="c3">B</font>
 <b>by </b><i><a class="ref" href="projpl_1.html#T7" target="_self" title="PROJPL_1:th.7">Th7</a></i>;<br/>
<b>consider </b><font color="Maroon" title="c4">a</font>, <font color="Maroon" title="c5">b</font> being   <a href="incsp_1.html#NM1" title="INCSP_1:NM.1">POINT</a> of <font color="Maroon" title="c1">G</font><b> such that </b><br/><a NAME="E5:22"/><i><font color="Green" title="E22">A3</font></i>: 
( <font color="Maroon" title="c4">a</font> <a href="incsp_1.html#R1" title="INCSP_1:pred.1">on</a> <font color="Maroon" title="c2">A</font> &amp; <font color="Maroon" title="c4">a</font> <a href="projpl_1.html#NR1" title="PROJPL_1:NR.1">|'</a> <font color="Maroon" title="c3">B</font> &amp; <font color="Maroon" title="c5">b</font> <a href="incsp_1.html#R1" title="INCSP_1:pred.1">on</a> <font color="Maroon" title="c3">B</font> &amp; <font color="Maroon" title="c5">b</font> <a href="projpl_1.html#NR1" title="PROJPL_1:NR.1">|'</a> <font color="Maroon" title="c2">A</font> )
 <b>by </b><i><a class="txt" href="projpl_1.html#E1:22"><i><font color="Green" title="E20">A1</font></i></a>, <a class="txt" href="projpl_1.html#E3:22"><i><font color="Green" title="E21">A2</font></i></a>, <a class="ref" href="projred1.html#T3" title="PROJRED1:th.3">PROJRED1:3</a></i>;<br/>
<b>consider </b><font color="Maroon" title="c6">p</font> being   <a href="incsp_1.html#NM1" title="INCSP_1:NM.1">POINT</a> of <font color="Maroon" title="c1">G</font><b> such that </b><br/><a NAME="E7:22"/><i><font color="Green" title="E23">A4</font></i>: 
( <font color="Maroon" title="c6">p</font> <a href="incsp_1.html#R1" title="INCSP_1:pred.1">on</a> <font color="Maroon" title="c2">A</font> &amp; <font color="Maroon" title="c6">p</font> <a href="projpl_1.html#NR1" title="PROJPL_1:NR.1">|'</a> <font color="Maroon" title="c3">B</font> &amp; <font color="Maroon" title="c4">a</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a> <font color="Maroon" title="c6">p</font> )
 <b>by </b><i><a class="txt" href="projpl_1.html#E1:22"><i><font color="Green" title="E20">A1</font></i></a>, <a class="txt" href="projpl_1.html#E5:22"><i><font color="Green" title="E22">A3</font></i></a>, <a class="ref" href="projpl_1.html#T9" target="_self" title="PROJPL_1:th.9">Th9</a></i>;<br/>
<b>consider </b><font color="Maroon" title="c7">q</font> being   <a href="incsp_1.html#NM1" title="INCSP_1:NM.1">POINT</a> of <font color="Maroon" title="c1">G</font><b> such that </b><br/><a NAME="E9:22"/><i><font color="Green" title="E24">A5</font></i>: 
( <font color="Maroon" title="c7">q</font> <a href="incsp_1.html#R1" title="INCSP_1:pred.1">on</a> <font color="Maroon" title="c3">B</font> &amp; <font color="Maroon" title="c7">q</font> <a href="projpl_1.html#NR1" title="PROJPL_1:NR.1">|'</a> <font color="Maroon" title="c2">A</font> &amp; <font color="Maroon" title="c5">b</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a> <font color="Maroon" title="c7">q</font> )
 <b>by </b><i><a class="txt" href="projpl_1.html#E1:22"><i><font color="Green" title="E20">A1</font></i></a>, <a class="txt" href="projpl_1.html#E5:22"><i><font color="Green" title="E22">A3</font></i></a>, <a class="ref" href="projpl_1.html#T9" target="_self" title="PROJPL_1:th.9">Th9</a></i>;<br/>
<a NAME="E10:22"/><i><font color="Green" title="E25">A6</font></i>: 
<font color="Maroon" title="c1">G</font> is <a href="projpl_1.html#V1" title="PROJPL_1:attr.1">configuration</a>
 
<b>by </b><i><a class="txt" href="projpl_1.html#E1:22"><i><font color="Green" title="E20">A1</font></i></a>, <a class="ref" href="projpl_1.html#T4" target="_self" title="PROJPL_1:th.4">Th4</a></i>;<br/>
<b>take </b>
<font color="Maroon" title="c4">a</font>
;<br/>

<b>take </b>
<font color="Maroon" title="c6">p</font>
;<br/>

<b>take </b>
<font color="Maroon" title="c5">b</font>
;<br/>

<b>take </b>
<font color="Maroon" title="c7">q</font>
;<br/>

<a NAME="E11:22"/><i><font color="Green" title="E26">A7</font></i>: 
( <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c6">p</font> <a href="incproj.html#R3" title="INCPROJ:pred.3">on</a> <font color="Maroon" title="c2">A</font> &amp; <font color="Maroon" title="c5">b</font>,<font color="Maroon" title="c7">q</font> <a href="incproj.html#R3" title="INCPROJ:pred.3">on</a> <font color="Maroon" title="c3">B</font> )
 
<b>by </b><i><a class="txt" href="projpl_1.html#E5:22"><i><font color="Green" title="E22">A3</font></i></a>, <a class="txt" href="projpl_1.html#E7:22"><i><font color="Green" title="E23">A4</font></i></a>, <a class="txt" href="projpl_1.html#E9:22"><i><font color="Green" title="E24">A5</font></i></a>, <a class="ref" href="incproj.html#D7" title="INCPROJ:def.7">INCPROJ:def 7</a></i>;<br/>
<a NAME="E12:22"/>
( <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c6">p</font> <a href="projpl_1.html#R1" title="PROJPL_1:pred.1">|'</a> <font color="Maroon" title="c3">B</font> &amp; <font color="Maroon" title="c5">b</font>,<font color="Maroon" title="c7">q</font> <a href="projpl_1.html#R1" title="PROJPL_1:pred.1">|'</a> <font color="Maroon" title="c2">A</font> )
 
<b>by </b><i><a class="txt" href="projpl_1.html#E5:22"><i><font color="Green" title="E22">A3</font></i></a>, <a class="txt" href="projpl_1.html#E7:22"><i><font color="Green" title="E23">A4</font></i></a>, <a class="txt" href="projpl_1.html#E9:22"><i><font color="Green" title="E24">A5</font></i></a>, <a class="ref" href="projpl_1.html#D1" target="_self" title="PROJPL_1:def.1">Def1</a></i>;<br/>
<b>hence </b><a NAME="E13:22"/>
<font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c6">p</font>,<font color="Maroon" title="c5">b</font>,<font color="Maroon" title="c7">q</font> <a href="projpl_1.html#R5" title="PROJPL_1:pred.5">is_a_quadrangle</a> 
 <b>by </b><i><a class="txt" href="projpl_1.html#E7:22"><i><font color="Green" title="E23">A4</font></i></a>, <a class="txt" href="projpl_1.html#E9:22"><i><font color="Green" title="E24">A5</font></i></a>, <a class="txt" href="projpl_1.html#E10:22"><i><font color="Green" title="E25">A6</font></i></a>, <a class="txt" href="projpl_1.html#E11:22"><i><font color="Green" title="E26">A7</font></i></a>, <a class="ref" href="projpl_1.html#T14" target="_self" title="PROJPL_1:th.14">Th14</a></i>;<br/>


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