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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E31">Th28</font></span>: <a NAME="T33"><span class="comment"><font color="firebrick">:: MODAL_1:33</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">A</font>, <font color="Olive" title="b2">B</font> being   <a href="modal_1.html#NM3" title="MODAL_1:NM.3">MP-wff</a>  st  <a href="modal_1.html#K10" title="MODAL_1:func.10">'not'</a> <font color="Olive" title="b1">A</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="modal_1.html#K10" title="MODAL_1:func.10">'not'</a> <font color="Olive" title="b2">B</font> holds <br/><font color="Olive" title="b1">A</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Olive" title="b2">B</font></div></div>
