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<div><span class="kw">theorem </span><a NAME="T18"><span class="comment"><font color="firebrick">:: DOMAIN_1:18</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">X1</font> being   non  <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>   <a href="hidden.html#M2" title="HIDDEN:mode.2">set</a>  holds  <font color="Olive" title="b1">X1</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1"> { <span class="default"> <font color="Olive" title="b2">x1</font> where <font color="Olive" title="b2">x1</font> is    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Olive" title="b1">X1</font> : verum </span> } </span> </div></div>
