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<div><span class="kw">theorem </span><a NAME="T21"><span class="comment"><font color="firebrick">:: INTERVA1:21</font></span><br/></a><div class="add"> for <font color="Olive" title="b1">U</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">A</font>, <font color="Olive" title="b3">B</font> being   non  <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>   <a href="interva1.html#M1" title="INTERVA1:mode.1">IntervalSet</a> of <font color="Olive" title="b1">U</font> holds  <font color="Olive" title="b2">A</font> <a href="interva1.html#K4" title="INTERVA1:func.4">_\/_</a> <font color="Olive" title="b3">B</font> <a href="interva1.html#R1" title="INTERVA1:pred.1">=</a> <font color="Olive" title="b3">B</font> <a href="interva1.html#K4" title="INTERVA1:func.4">_\/_</a> <font color="Olive" title="b2">A</font> ;<br/></div></div>
