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<b>let </b><font color="Maroon" title="c1">AS</font> be   <a href="diraf.html#NM1" title="DIRAF:NM.1">AffinSpace</a>;<br/><b>let </b><font color="Maroon" title="c2">a</font> be   <a href="struct_0.html#NM1" title="STRUCT_0:NM.1">Element</a> of <font color="Maroon" title="c1">AS</font>;<br/><b>let </b><font color="Maroon" title="c3">X</font> be   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">AS</font>;<br/>





<b>assume </b><a NAME="E1:84"/><i><font color="Green" title="E68">A1</font></i>: 
<font color="Maroon" title="c3">X</font> <a href="aff_4.html#NR1" title="AFF_4:NR.1">is_plane</a> 
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="84_1"><b>now </b></a><div class="add"><b>assume </b><a NAME="E1:84_1"/>
<font color="Maroon" title="c2">a</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c3">X</font>
 ;<br/><a NAME="E2:84_1"/><b>then </b>
( <font color="Maroon" title="c2">a</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c3">X</font> &amp; <font color="Maroon" title="c3">X</font> <a href="aff_4.html#R1" title="AFF_4:pred.1">'||'</a> <font color="Maroon" title="c3">X</font> )
 <b>by </b><i><a class="txt" href="aff_4.html#E1:84"><i><font color="Green" title="E68">A1</font></i></a>, <a class="ref" href="aff_4.html#T57" target="_self" title="AFF_4:th.57">Th57</a></i>;<br/><b>hence </b><a NAME="E3:84_1"/>
<font color="Maroon" title="c2">a</font> <a href="aff_4.html#K3" title="AFF_4:func.3">+</a> <font color="Maroon" title="c3">X</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c3">X</font>
 <b>by </b><i><a class="txt" href="aff_4.html#E1:84"><i><font color="Green" title="E68">A1</font></i></a>, <a class="ref" href="aff_4.html#D6" target="_self" title="AFF_4:def.6">Def6</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E3:84"/>
( <font color="Maroon" title="c2">a</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c3">X</font> iff <font color="Maroon" title="c2">a</font> <a href="aff_4.html#K3" title="AFF_4:func.3">+</a> <font color="Maroon" title="c3">X</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c3">X</font> )
 <b>by </b><i><a class="txt" href="aff_4.html#E1:84"><i><font color="Green" title="E68">A1</font></i></a>, <a class="ref" href="aff_4.html#D6" target="_self" title="AFF_4:def.6">Def6</a></i>;<br/>


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