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<div><span class="kw">theorem </span><a NAME="T16"><span class="comment"><font color="firebrick">:: FUNCT_5:16</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>  holds <br/> (  <a href="xtuple_0.html#K9" title="XTUPLE_0:func.9">proj1</a> <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>  iff  <a href="xtuple_0.html#K10" title="XTUPLE_0:func.10">proj2</a> <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>  )</div></div>
