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<div><span class="kw">theorem </span><a NAME="T23"><span class="comment"><font color="firebrick">:: FINANCE5:23</font></span><br/></a><div class="add"> <a href="prob_1.html#K11" title="PROB_1:func.11">Family_of_halflines</a>  <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="finance5.html#K9" title="FINANCE5:func.9">Ext_Borel_Sets</a> </div></div>
