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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">A</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">S</font>;<br/><b>let </b><font color="Maroon">B</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">S</font>;<br/><b>let </b><font color="Maroon">C</font> be   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">S</font>;<br/>







<b>set </b><font color="Maroon">P2</font> =  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span>;<br/>
<b>set </b><font color="Maroon">L1</font> =  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/>
<b>set </b><font color="Maroon">L2</font> =  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font>;<br/>
<b>assume </b><a NAME="E1:62"/><i><font color="Green">E23</font></i>: 
not <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/>

<a NAME="E2:62"/><b>then </b>
not <span class="p1"><a href="domain_1.html#K8">{</a><span class="default"><font color="Maroon">A</font>,<font color="Maroon">C</font>,<font color="Maroon">B</font></span><a href="domain_1.html#K8">}</a></span> <a href="incsp_1.html#NR6" target="_self">is_collinear</a> 
 
<b>by </b><i><a class="ref" href="enumset1.html#T98">ENUMSET1:98</a></i>;<br/>
<a NAME="E3:62"/><b>then </b><i><font color="Green">E24</font></i>: 
( <font color="Maroon">A</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">B</font> &amp; <font color="Maroon">A</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">C</font> )
 
<b>by </b><i>, <a class="ref" href="incsp_1.html#D7" target="_self">Def7</a></i>;<br/>
<a NAME="E4:62"/><b>then </b><i><font color="Green">E36</font></i>: 
( <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>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</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>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font> )
 
<b>by </b><i><a class="ref" href="incsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<a NAME="E5:62"/><b>then </b><i><font color="Green">E57</font></i>: 
( <font color="Maroon">A</font> <a href="incsp_1.html#R1" target="_self">on</a>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font> &amp; <font color="Maroon">A</font> <a href="incsp_1.html#R1" target="_self">on</a>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font> )
 
<b>by </b><i/>;<br/>
<a NAME="E6:62"/>
<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>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font>
 
<b>by </b><i>, <a class="ref" href="incsp_1.html#T17" target="_self">Th17</a></i>;<br/>
<a NAME="E7:62"/><b>then </b>
<font color="Maroon">C</font> <a href="incsp_1.html#R1" target="_self">on</a>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font>
 
<b>by </b><i/>;<br/>
<a NAME="E8:62"/><b>then </b>
 <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font>
 
<b>by </b><i>, , <a class="ref" href="incsp_1.html#D8" target="_self">Def8</a></i>;<br/>
<a NAME="E9:62"/><b>then </b>
(  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font> <a href="incsp_1.html#R3" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span> &amp;  <a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font> <a href="incsp_1.html#R3" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span> )
 
<b>by </b><i>, <a class="ref" href="incsp_1.html#T20" target="_self">Th20</a></i>;<br/>
<a NAME="E10:62"/><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#R5" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span> &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#R5" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span> )
 
<b>by </b><i>, <a class="ref" href="incsp_1.html#D6" target="_self">Def6</a></i>;<br/>
<a NAME="E11:62"/><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#R5" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span> &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> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span> )
 
<b>by </b><i/>;<br/>
<a NAME="E12:62"/><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="subset_1.html#K4">\/</a> <span class="p1"><a href="domain_1.html#K6">{</a><span class="default"><font color="Maroon">C</font></span><a href="domain_1.html#K6">}</a></span> <a href="incsp_1.html#R5" target="_self">on</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span>
 
<b>by </b><i><a class="ref" href="incsp_1.html#D2" target="_self">Def2</a></i>;<br/>
<a NAME="E13:62"/><b>then </b>
<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> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span>
 
<b>by </b><i><a class="ref" href="enumset1.html#T43">ENUMSET1:43</a></i>;<br/>
<b>hence </b><a NAME="E14:62"/>
 <a href="incsp_1.html#K2" target="_self">Plane</a> <font color="Maroon">A</font>,<font color="Maroon">B</font>,<font color="Maroon">C</font> <a href="hidden.html#R1">=</a>  <a href="incsp_1.html#K4" target="_self">Plane</a> <span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">B</font></span>)</span>,<span class="p1">(<span class="default"><a href="incsp_1.html#K1" target="_self">Line</a> <font color="Maroon">A</font>,<font color="Maroon">C</font></span>)</span>
 <b>by </b><i>, <a class="ref" href="incsp_1.html#T18" target="_self">Th18</a></i>;<br/>


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