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<b>let </b><font color="Maroon">S</font> be   <a href="incsp_1.html#NM4">IncSpace</a>;<br/><b>let </b><font color="Maroon">K</font> be   <a href="incsp_1.html#NM2">LINE</a> of <font color="Maroon">S</font>;<br/><b>let </b><font color="Maroon">L</font> be   <a href="incsp_1.html#NM2">LINE</a> of <font color="Maroon">S</font>;<br/>





<b>assume </b><a NAME="E1:56"/><i><font color="Green">E23</font></i>: 
<font color="Maroon">K</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">L</font>
 ;<br/>

<b>given </b><font color="Maroon">A</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">S</font><b> such that </b><a NAME="E2:56"/><i><font color="Green">E24</font></i>: 
( <font color="Maroon">A</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">K</font> &amp; <font color="Maroon">A</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">L</font> )
 ;<br/>

<b>consider </b><font color="Maroon">B</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">S</font><b> such that </b><br/><a NAME="E4:56"/><i><font color="Green">E36</font></i>: 
<font color="Maroon">A</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">B</font>
 <b>and </b><br/><a NAME="E5:56"/><i><font color="Green">E57</font></i>: 
<font color="Maroon">B</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">K</font>
 <b>by </b><i><a class="ref" href="incsp_1.html#T13" target="_self">Th13</a></i>;<br/>
<b>consider </b><font color="Maroon">C</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">S</font><b> such that </b><br/><a NAME="E7:56"/><i><font color="Green">E58</font></i>: 
<font color="Maroon">A</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">C</font>
 <b>and </b><br/><a NAME="E8:56"/><i><font color="Green">E60</font></i>: 
<font color="Maroon">C</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">L</font>
 <b>by </b><i><a class="ref" href="incsp_1.html#T13" target="_self">Th13</a></i>;<br/>
<b>set </b><font color="Maroon">P1</font> =  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font>;<br/>
<b>set </b><font color="Maroon">P2</font> =  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font>;<br/>
<a NAME="E9:56"/>
( <font color="Maroon">K</font> <a href="incsp_1.html#R3" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> &amp; <font color="Maroon">L</font> <a href="incsp_1.html#R3" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> &amp; <font color="Maroon">K</font> <a href="incsp_1.html#R3" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font> &amp; <font color="Maroon">L</font> <a href="incsp_1.html#R3" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font> )
 
<b>by </b><i><a class="ref" href="incsp_1.html#D8" target="_self">Def8</a>, , <a class="ref" href="incsp_1.html#T20" target="_self">Th20</a></i>;<br/>
<a NAME="E10:56"/><b>then </b>
( <font color="Maroon">A</font> <a href="incsp_1.html#R2" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> &amp; <font color="Maroon">B</font> <a href="incsp_1.html#R2" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> &amp; <font color="Maroon">C</font> <a href="incsp_1.html#R2" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> &amp; <font color="Maroon">A</font> <a href="incsp_1.html#R2" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font> &amp; <font color="Maroon">B</font> <a href="incsp_1.html#R2" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font> &amp; <font color="Maroon">C</font> <a href="incsp_1.html#R2" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font> )
 
<b>by </b><i>, , , <a class="ref" href="incsp_1.html#D5" target="_self">Def5</a></i>;<br/>
<a NAME="E11:56"/><b>then </b><i><font color="Green">E61</font></i>: 
( <span class="p1"><a href="domain_1.html#K8">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">B</font>,<font color="Maroon">C</font></span><a href="domain_1.html#K8">}</a></span> <a href="incsp_1.html#R5" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> &amp; <span class="p1"><a href="domain_1.html#K8">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">B</font>,<font color="Maroon">C</font></span><a href="domain_1.html#K8">}</a></span> <a href="incsp_1.html#R5" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font> )
 
<b>by </b><i/>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="56_1"><b>now </b></a><div class="add"><b>assume </b><a NAME="E1:56_1"/>
<span class="p1"><a href="domain_1.html#K8">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">B</font>,<font color="Maroon">C</font></span><a href="domain_1.html#K8">}</a></span> <a href="incsp_1.html#NR6" target="_self">is_collinear</a> 
 ;<br/><b>then consider </b><font color="Maroon">L1</font> being   <a href="incsp_1.html#NM2">LINE</a> of <font color="Maroon">S</font><b> such that </b><br/><a NAME="E3:56_1"/><i><font color="Green">E62</font></i>: 
<span class="p1"><a href="domain_1.html#K8">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">B</font>,<font color="Maroon">C</font></span><a href="domain_1.html#K8">}</a></span> <a href="incsp_1.html#R4" target="_self">on</a> <font color="Maroon">L1</font>
 <b>by </b><i/>;<br/><a NAME="E4:56_1"/>
( <font color="Maroon">A</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">L1</font> &amp; <font color="Maroon">B</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">L1</font> &amp; <font color="Maroon">C</font> <a href="incsp_1.html#R1" target="_self">on</a> <font color="Maroon">L1</font> )
 <b>by </b><i>, </i>;<br/><a NAME="E5:56_1"/><b>then </b>
( <span class="p1"><a href="domain_1.html#K7">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">B</font></span><a href="domain_1.html#K7">}</a></span> <a href="incsp_1.html#R4" target="_self">on</a> <font color="Maroon">L1</font> &amp; <span class="p1"><a href="domain_1.html#K7">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">B</font></span><a href="domain_1.html#K7">}</a></span> <a href="incsp_1.html#R4" target="_self">on</a> <font color="Maroon">K</font> &amp; <span class="p1"><a href="domain_1.html#K7">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">C</font></span><a href="domain_1.html#K7">}</a></span> <a href="incsp_1.html#R4" target="_self">on</a> <font color="Maroon">L1</font> &amp; <span class="p1"><a href="domain_1.html#K7">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">C</font></span><a href="domain_1.html#K7">}</a></span> <a href="incsp_1.html#R4" target="_self">on</a> <font color="Maroon">L</font> )
 <b>by </b><i>, , , </i>;<br/><a NAME="E6:56_1"/><b>then </b>
( <font color="Maroon">K</font> <a href="hidden.html#R1">=</a> <font color="Maroon">L1</font> &amp; <font color="Maroon">L</font> <a href="hidden.html#R1">=</a> <font color="Maroon">L1</font> )
 <b>by </b><i>, , <a class="ref" href="incsp_1.html#D5" target="_self">Def5</a></i>;<br/><b>hence </b><a NAME="E7:56_1"/>
contradiction
 <b>by </b><i><a class="ref" href="incsp_1.html#D8" target="_self">Def8</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E13:56"/>
 <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">K</font>,<font color="Maroon">L</font> <a href="hidden.html#R1">=</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <font color="Maroon">L</font>,<font color="Maroon">K</font>
 <b>by </b><i>, <a class="ref" href="incsp_1.html#D5" target="_self">Def5</a></i>;<br/>


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