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<b>let </b><font color="Maroon" title="c1">M</font> be   <a href="sub_metr.html#NM1" title="SUB_METR:NM.1">PseudoMetricSpace</a>;<br/><b>let </b><font color="Maroon" title="c2">V</font>, <font color="Maroon" title="c3">Q</font> be    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Maroon" title="c1">M</font> <a href="metric_2.html#K2" title="METRIC_2:func.2">-neighbour</a> ;<br/><b>let </b><font color="Maroon" title="c4">v</font> be    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of  <a href="numbers.html#K1" title="NUMBERS:func.1">REAL</a> ;<br/>





<a NAME="E1:33"/><i><font color="Green" title="E20">A1</font></i>: 
( <font color="Maroon" title="c4">v</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="metric_2.html#K3" title="METRIC_2:func.3">ev_eq_1</a> <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> implies <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> <a href="metric_2.html#R4" title="METRIC_2:pred.4">is_dst</a> <font color="Maroon" title="c4">v</font> )
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="33_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:33_1"/>
<font color="Maroon" title="c4">v</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="metric_2.html#K3" title="METRIC_2:func.3">ev_eq_1</a> <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font>
 ;<br/>

<a NAME="E2:33_1"/><b>then </b>
<font color="Maroon" title="c4">v</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <span class="p1">{<span class="default"> <font color="Olive" title="b1">r</font> where <font color="Olive" title="b1">r</font> is    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of  <a href="numbers.html#K1" title="NUMBERS:func.1">REAL</a>  : <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> <a href="metric_2.html#R4" title="METRIC_2:pred.4">is_dst</a> <font color="Olive" title="b1">r</font> </span>}</span> 
 
;<br/>
<a NAME="E3:33_1"/><b>then </b>
 ex <font color="Olive" title="b1">r</font> being   <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of  <a href="numbers.html#K1" title="NUMBERS:func.1">REAL</a>  st <br/>( <font color="Olive" title="b1">r</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c4">v</font> &amp; <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> <a href="metric_2.html#R4" title="METRIC_2:pred.4">is_dst</a> <font color="Olive" title="b1">r</font> )
 
;<br/>
<b>hence </b><a NAME="E4:33_1"/>
<font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> <a href="metric_2.html#R4" title="METRIC_2:pred.4">is_dst</a> <font color="Maroon" title="c4">v</font>
 ;<br/>


</div><b>end;</b></div>
<b>thus </b><a NAME="E2:33"/>
( <font color="Maroon" title="c4">v</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="metric_2.html#K3" title="METRIC_2:func.3">ev_eq_1</a> <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> iff <font color="Maroon" title="c2">V</font>,<font color="Maroon" title="c3">Q</font> <a href="metric_2.html#R4" title="METRIC_2:pred.4">is_dst</a> <font color="Maroon" title="c4">v</font> )
 <b>by </b><i><a class="txt" href="metric_2.html#E1:33"><i><font color="Green" title="E20">A1</font></i></a></i>;<br/>


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