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<b>let </b><font color="Maroon">N</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="metric_1.html#L1">MetrStruct</a> ;<br/><b>let </b><font color="Maroon">C</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">N</font>;<br/>



<b>thus </b><a NAME="E1:23"/>
( <font color="Maroon">C</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">C</font> is <a href="tbsp_1.html#V6" target="_self">bounded</a> implies  ex <font color="Olive">r</font> being  <a href="real_1.html#NM1">Real</a> ex <font color="Olive">w</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">N</font> st <br/>( 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Olive">r</font> &amp; <font color="Olive">w</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> &amp; ( for <font color="Olive">z</font> being  <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>  st <font color="Olive">z</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> holds <br/> <a href="metric_1.html#K2">dist</a> <font color="Olive">w</font>,<font color="Olive">z</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Olive">r</font> ) ) )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="23_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:23_1"/><i><font color="Green">E44</font></i>: 
<font color="Maroon">C</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<b>assume </b><a NAME="E2:23_1"/>
<font color="Maroon">C</font> is <a href="tbsp_1.html#V6" target="_self">bounded</a>
 ;<br/>

<b>then consider </b><font color="Maroon">r</font> being   <a href="real_1.html#NM1">Real</a><b> such that </b><br/><a NAME="E4:23_1"/><i><font color="Green">E45</font></i>: 
( 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Maroon">r</font> &amp; ( for <font color="Olive">x</font>, <font color="Olive">y</font> being  <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>  st <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> &amp; <font color="Olive">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> holds <br/> <a href="metric_1.html#K2">dist</a> <font color="Olive">x</font>,<font color="Olive">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> ) )
 <b>by </b><i/>;<br/>
<b>take </b>
<font color="Maroon">r</font>
;<br/>

<b>consider </b><font color="Maroon">w</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">C</font>;<br/>
<b>reconsider </b><font color="Maroon">w</font> = <font color="Maroon">w</font> as   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font> <b>by </b><i>, <a class="ref" href="tarski.html#D3">TARSKI:def 3</a></i>;<br/>
<b>take </b>
<font color="Maroon">w</font>
;<br/>

<b>thus </b><a NAME="E7:23_1"/>
0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Maroon">r</font>
 <b>by </b><i/>;<br/>

<b>thus </b><a NAME="E8:23_1"/>
<font color="Maroon">w</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font>
 <b>by </b><i/>;<br/>

<b>let </b><font color="Maroon">z</font> be   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>;<br/>

<b>assume </b><a NAME="E9:23_1"/>
<font color="Maroon">z</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font>
 ;<br/>

<b>hence </b><a NAME="E10:23_1"/>
 <a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Maroon">z</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font>
 <b>by </b><i/>;<br/>


</div><b>end;</b></div>

<b>assume </b><a NAME="E2:23"/><i><font color="Green">E48</font></i>: 
<font color="Maroon">N</font> is <a href="metric_1.html#V8">symmetric</a>
 ;<br/>

<b>assume </b><a NAME="E3:23"/><i><font color="Green">E49</font></i>: 
<font color="Maroon">N</font> is <a href="metric_1.html#V9">triangle</a>
 ;<br/>

<b>given </b><font color="Maroon">r</font> being   <a href="real_1.html#NM1">Real</a>, <font color="Maroon">w</font> being   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">N</font><b> such that </b><a NAME="E4:23"/><i><font color="Green">E50</font></i>: 
( 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Maroon">r</font> &amp; <font color="Maroon">w</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> &amp; ( for <font color="Olive">z</font> being  <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>  st <font color="Olive">z</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> holds <br/> <a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Olive">z</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> ) )
 ;<br/>

<b>set </b><font color="Maroon">s</font> = <font color="Maroon">r</font> <a href="real_1.html#K3">+</a> <font color="Maroon">r</font>;<br/>
<a NAME="E5:23"/><i><font color="Green">E54</font></i>: 
<font color="Maroon">r</font> <a href="real_1.html#K3">+</a> <font color="Maroon">r</font> <a href="hidden.html#R1">=</a> 2 <a href="real_1.html#K4">*</a> <font color="Maroon">r</font>
 
;<br/>
<a NAME="E6:23"/>
 ex <font color="Olive">s</font> being  <a href="real_1.html#NM1">Real</a> st <br/>( 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Olive">s</font> &amp; ( for <font color="Olive">x</font>, <font color="Olive">y</font> being  <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>  st <font color="Olive">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> &amp; <font color="Olive">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> holds <br/> <a href="metric_1.html#K2">dist</a> <font color="Olive">x</font>,<font color="Olive">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Olive">s</font> ) )
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="23_2"><b>proof </b></a><div class="add">

<b>take </b>
<font color="Maroon">r</font> <a href="real_1.html#K3">+</a> <font color="Maroon">r</font>
;<br/>

<b>thus </b><a NAME="E1:23_2"/>
0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a> <font color="Maroon">r</font> <a href="real_1.html#K3">+</a> <font color="Maroon">r</font>
 <b>by </b><i>, , <a class="ref" href="real_2.html#T122">REAL_2:122</a></i>;<br/>

<b>let </b><font color="Maroon">x</font> be   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>, <font color="Maroon">y</font> be   <a href="pre_topc.html#NM2">Point</a> of <font color="Maroon">N</font>;<br/>

<b>assume </b><a NAME="E2:23_2"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> &amp; <font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">C</font> )
 ;<br/>

<a NAME="E3:23_2"/><b>then </b>
(  <a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Maroon">x</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> &amp;  <a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Maroon">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> )
 
<b>by </b><i/>;<br/>
<a NAME="E4:23_2"/><b>then </b>
(  <a href="metric_1.html#K2">dist</a> <font color="Maroon">x</font>,<font color="Maroon">w</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> &amp;  <a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Maroon">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> )
 
<b>by </b><i>, <a class="ref" href="metric_1.html#T3">METRIC_1:3</a></i>;<br/>
<a NAME="E5:23_2"/><b>then </b><i><font color="Green">E60</font></i>: 
<span class="p1">(<span class="default"><a href="metric_1.html#K2">dist</a> <font color="Maroon">x</font>,<font color="Maroon">w</font></span>)</span> <a href="real_1.html#K3">+</a> <span class="p1">(<span class="default"><a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Maroon">y</font></span>)</span> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> <a href="real_1.html#K3">+</a> <font color="Maroon">r</font>
 
<b>by </b><i><a class="ref" href="xreal_1.html#T9">XREAL_1:9</a></i>;<br/>
<a NAME="E6:23_2"/>
 <a href="metric_1.html#K2">dist</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <span class="p1">(<span class="default"><a href="metric_1.html#K2">dist</a> <font color="Maroon">x</font>,<font color="Maroon">w</font></span>)</span> <a href="real_1.html#K3">+</a> <span class="p1">(<span class="default"><a href="metric_1.html#K2">dist</a> <font color="Maroon">w</font>,<font color="Maroon">y</font></span>)</span>
 
<b>by </b><i>, <a class="ref" href="metric_1.html#T4">METRIC_1:4</a></i>;<br/>
<b>hence </b><a NAME="E7:23_2"/>
 <a href="metric_1.html#K2">dist</a> <font color="Maroon">x</font>,<font color="Maroon">y</font> <a href="xxreal_0.html#R1">&lt;=</a> <font color="Maroon">r</font> <a href="real_1.html#K3">+</a> <font color="Maroon">r</font>
 <b>by </b><i>, <a class="ref" href="xxreal_0.html#T2">XXREAL_0:2</a></i>;<br/>


</div><b>end;</b></div>
<b>hence </b><a NAME="E7:23"/>
<font color="Maroon">C</font> is <a href="tbsp_1.html#V6" target="_self">bounded</a>
 <b>by </b><i/>;<br/>


</div>
