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<b>let </b><font color="Maroon">M</font> be   <a href="midsp_1.html#NM1">MidSp</a>;<br/><b>let </b><font color="Maroon">p</font> be   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">M</font>;<br/><b>let </b><font color="Maroon">q</font> be   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">M</font>;<br/><b>let </b><font color="Maroon">r</font> be   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">M</font>;<br/>







<a NAME="E1:35"/>
( <font color="Maroon">p</font> <a href="midsp_1.html#K4">@</a> <font color="Maroon">q</font> <a href="hidden.html#R1">=</a> <font color="Maroon">r</font> iff <font color="Maroon">p</font> <a href="midsp_1.html#K4">@</a> <font color="Maroon">q</font> <a href="hidden.html#R1">=</a> <font color="Maroon">r</font> <a href="midsp_1.html#K4">@</a> <font color="Maroon">r</font> )
 
<b>by </b><i><a class="ref" href="midsp_1.html#D4">MIDSP_1:def 4</a></i>;<br/>
<b>hence </b><a NAME="E2:35"/>
( <font color="Maroon">p</font> <a href="midsp_1.html#K4">@</a> <font color="Maroon">q</font> <a href="hidden.html#R1">=</a> <font color="Maroon">r</font> iff  <a href="midsp_1.html#K11">vect</a> <font color="Maroon">p</font>,<font color="Maroon">r</font> <a href="hidden.html#R1">=</a>  <a href="midsp_1.html#K11">vect</a> <font color="Maroon">r</font>,<font color="Maroon">q</font> )
 <b>by </b><i/>;<br/>


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