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<div><span class="kw">theorem </span><a NAME="T6"><span class="comment"><font color="firebrick">:: BOOLE:6</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">X</font> being    <a href="hidden.html#M2" title="HIDDEN:mode.2">set</a>   st <font color="Olive" title="b1">X</font> is  <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>  holds <br/><font color="Olive" title="b1">X</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  <span class="kw">by</span> <span class="lab"><a class="txt" href="boole.html#E6"><span class="lab"><font color="Green" title="E1">Lm1</font></span></a></span>;<br/></div></div>
