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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E16">Th18</font></span>: <a NAME="T18"><span class="comment"><font color="firebrick">:: XXREAL_1:18</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">r</font> being   <a href="xxreal_0.html#NM1" title="XXREAL_0:NM.1">ExtReal</a> holds  <span class="p1"><a href="xxreal_1.html#K2" title="XXREAL_1:func.2">[.</a><span class="default"><font color="Olive" title="b1">r</font>,<font color="Olive" title="b1">r</font></span><a href="xxreal_1.html#K2" title="XXREAL_1:func.2">.[</a></span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> </div></div>
