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<div><span class="kw">theorem </span><a NAME="T2"><span class="comment"><font color="firebrick">:: ZFMISC_1:2</font></span><br/></a><div class="add"> <a href="tarski.html#K3" title="TARSKI:func.3">union</a> <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> </div></div>
