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<b>consider </b><font color="Maroon">a</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>, <font color="Maroon">b</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>, <font color="Maroon">c</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font>, <font color="Maroon">d</font> being   <a href="incsp_1.html#NM1">POINT</a> of <font color="Maroon">G</font><b> such that </b><br/><a NAME="E2:23_1_1"/><i><font color="Green">E36</font></i>: 
<font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font>,<font color="Maroon">d</font> <a href="projpl_1.html#R5" target="_self">is_a_quadrangle</a> 
 <b>by </b><i/>;<br/>
<b>reconsider </b><font color="Maroon">e</font> = <span class="p1"><a href="domain_1.html#K5">[</a><span class="default"><font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font>,<font color="Maroon">d</font></span><a href="domain_1.html#K5">]</a></span> as    <a href="subset_1.html#M1">Element</a> of <span class="p1"><a href="zfmisc_1.html#K4">[:</a><span class="default">the <a href="incsp_1.html#U1">Points</a> of <font color="Maroon">G</font>,the <a href="incsp_1.html#U1">Points</a> of <font color="Maroon">G</font>,the <a href="incsp_1.html#U1">Points</a> of <font color="Maroon">G</font>,the <a href="incsp_1.html#U1">Points</a> of <font color="Maroon">G</font></span><a href="zfmisc_1.html#K4">:]</a></span> ;<br/>
<a NAME="E4:23_1_1"/><i><font color="Green">E37</font></i>: 
( <font color="Maroon">e</font> <a href="mcart_1.html#K8">`1</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">a</font> &amp; <font color="Maroon">e</font> <a href="mcart_1.html#K9">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">b</font> &amp; <font color="Maroon">e</font> <a href="mcart_1.html#K10">`3</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">c</font> &amp; <font color="Maroon">e</font> <a href="mcart_1.html#K11">`4</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">d</font> )
 
<b>by </b><i><a class="ref" href="mcart_1.html#T59">MCART_1:59</a></i>;<br/>
<b>take </b>
<font color="Maroon">e</font>
;<br/>

<b>thus </b><a NAME="E5:23_1_1"/>
<font color="Maroon">e</font> <a href="mcart_1.html#K8">`1</a> ,<font color="Maroon">e</font> <a href="mcart_1.html#K9">`2</a> ,<font color="Maroon">e</font> <a href="mcart_1.html#K10">`3</a> ,<font color="Maroon">e</font> <a href="mcart_1.html#K11">`4</a>  <a href="projpl_1.html#R5" target="_self">is_a_quadrangle</a> 
 <b>by </b><i>, </i>;<br/>


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