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<b>let </b><font color="Maroon">FT</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="orders_2.html#L1">RelStr</a> ;<br/><b>let </b><font color="Maroon">A</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">FT</font>;<br/>



<b>assume </b><a NAME="E1:5"/>
for <font color="Olive">B</font>, <font color="Olive">C</font> being  <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">FT</font>  st <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Olive">B</font> <a href="subset_1.html#K4">\/</a> <font color="Olive">C</font> &amp; <font color="Olive">B</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Olive">C</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Olive">B</font> <a href="xboole_0.html#R1">misses</a> <font color="Olive">C</font> holds <br/>( <font color="Olive">B</font> <a href="fin_topo.html#K9">^b</a>  <a href="xboole_0.html#NR5" target="_self">meets</a> <font color="Olive">C</font> &amp; <font color="Olive">B</font> <a href="xboole_0.html#NR5" target="_self">meets</a> <font color="Olive">C</font> <a href="fin_topo.html#K9">^b</a>  )
 ;<br/>

<a NAME="E2:5"/><b>then </b>
for <font color="Olive">B</font>, <font color="Olive">C</font> being  <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">FT</font>  st <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Olive">B</font> <a href="subset_1.html#K4">\/</a> <font color="Olive">C</font> &amp; <font color="Olive">B</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Olive">C</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Olive">B</font> <a href="xboole_0.html#R1">misses</a> <font color="Olive">C</font> holds <br/><font color="Olive">B</font> <a href="fin_topo.html#K9">^b</a>  <a href="xboole_0.html#NR5" target="_self">meets</a> <font color="Olive">C</font>
 
;<br/>
<b>hence </b><a NAME="E3:5"/>
<font color="Maroon">A</font> is <a href="fin_topo.html#V5">connected</a>
 <b>by </b><i><a class="ref" href="fin_topo.html#D18">FIN_TOPO:def 18</a></i>;<br/>


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