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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E23">Th81</font></span>: <a NAME="T81"><span class="comment"><font color="firebrick">:: FUNCT_8:81</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">B</font> being   <a href="funct_8.html#V1" title="FUNCT_8:attr.1">symmetrical</a>  <a href="subset_1.html#NM2" title="SUBSET_1:NM.2">Subset</a> of <a href="numbers.html#K1" title="NUMBERS:func.1">REAL</a>  st <font color="Olive" title="b1">B</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="relset_1.html#K1" title="RELSET_1:func.1">dom</a> <a href="fdiff_9.html#K1" title="FDIFF_9:func.1">sec</a> holds <br/> <a href="fdiff_9.html#K1" title="FDIFF_9:func.1">sec</a>  <a href="funct_8.html#R1" title="FUNCT_8:pred.1">is_even_on</a> <font color="Olive" title="b1">B</font></div></div>
