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<b>let </b><font color="Maroon">p1</font> be   <a href="pre_topc.html#NM2">Point</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15">TOP-REAL</a> 2</span>)</span>;<br/><b>let </b><font color="Maroon">p2</font> be   <a href="pre_topc.html#NM2">Point</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15">TOP-REAL</a> 2</span>)</span>;<br/><b>let </b><font color="Maroon">p3</font> be   <a href="pre_topc.html#NM2">Point</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15">TOP-REAL</a> 2</span>)</span>;<br/>





<b>assume </b><a NAME="E1:39"/><i><font color="Green">E41</font></i>: 
 <a href="euclid_3.html#K4" target="_self">angle</a> <font color="Maroon">p1</font>,<font color="Maroon">p2</font>,<font color="Maroon">p3</font> <a href="hidden.html#R1">=</a> 0
 ;<br/>

<a NAME="E2:39"/><i><font color="Green">E49</font></i>: 
<span class="p1">(<span class="default"><a href="euclid_3.html#K2" target="_self">euc2cpx</a> <font color="Maroon">p1</font></span>)</span> <a href="complex1.html#K11">-</a> <span class="p1">(<span class="default"><a href="euclid_3.html#K2" target="_self">euc2cpx</a> <font color="Maroon">p2</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="euclid_3.html#K2" target="_self">euc2cpx</a> <span class="p1">(<span class="default"><font color="Maroon">p1</font> <a href="euclid.html#K20">-</a> <font color="Maroon">p2</font></span>)</span>
 
<b>by </b><i/>;<br/>
<a NAME="E3:39"/><i><font color="Green">E50</font></i>: 
<span class="p1">(<span class="default"><a href="euclid_3.html#K2" target="_self">euc2cpx</a> <font color="Maroon">p3</font></span>)</span> <a href="complex1.html#K11">-</a> <span class="p1">(<span class="default"><a href="euclid_3.html#K2" target="_self">euc2cpx</a> <font color="Maroon">p2</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="euclid_3.html#K2" target="_self">euc2cpx</a> <span class="p1">(<span class="default"><font color="Maroon">p3</font> <a href="euclid.html#K20">-</a> <font color="Maroon">p2</font></span>)</span>
 
<b>by </b><i/>;<br/>
<b>thus </b><a NAME="E4:39"/>
(  <a href="euclid_3.html#K3" target="_self">Arg</a> <span class="p1">(<span class="default"><font color="Maroon">p1</font> <a href="euclid.html#K20">-</a> <font color="Maroon">p2</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="euclid_3.html#K3" target="_self">Arg</a> <span class="p1">(<span class="default"><font color="Maroon">p3</font> <a href="euclid.html#K20">-</a> <font color="Maroon">p2</font></span>)</span> &amp;  <a href="euclid_3.html#K4" target="_self">angle</a> <font color="Maroon">p3</font>,<font color="Maroon">p2</font>,<font color="Maroon">p1</font> <a href="hidden.html#R1">=</a> 0 )
 <b>by </b><i>, , , <a class="ref" href="complex2.html#T88">COMPLEX2:88</a></i>;<br/>


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