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<a NAME="E1:15_1_1"/>
(  <a href="finseq_1.html#K3">len</a> <font color="Maroon">f</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> 0 &amp;  <a href="finseq_1.html#K3">len</a> <font color="Maroon">f</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> 1 )
 
<b>by </b><i><a class="ref" href="realset1.html#T13">REALSET1:13</a></i>;<br/>
<b>hence </b><a NAME="E2:15_1_1"/>
not  <a href="topreal1.html#K5">L~</a> <font color="Maroon">f</font> is <a href="xboole_0.html#V1">empty</a>
 <b>by </b><i><a class="ref" href="topreal1.html#T28">TOPREAL1:28</a></i>;<br/>


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