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<div><span class="kw">theorem </span><span class="lab"><font color="Green" title="E25">Th31</font></span>: <a NAME="T31"><span class="comment"><font color="firebrick">:: BSPACE:31</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">X</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> <br/>  for <font color="Olive" title="b2">x</font> being    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Olive" title="b1">X</font> holds  <span class="p1">(<span class="default"><a href="bspace.html#K1" title="BSPACE:func.1">&lt;*&gt;</a> <span class="p2">(<span class="default"><a href="bspace.html#K7" title="BSPACE:func.7">bspace</a> <font color="Olive" title="b1">X</font></span>)</span></span>)</span> <a href="bspace.html#K11" title="BSPACE:func.11">@</a> <font color="Olive" title="b2">x</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="bspace.html#K1" title="BSPACE:func.1">&lt;*&gt;</a> <a href="bspace.html#K2" title="BSPACE:func.2">Z_2</a></div></div>
