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<b>consider </b><font color="Maroon" title="c3">x</font> being    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> <b> such that </b><br/><a NAME="E2:8_1_1"/><i><font color="Green" title="E8">A1</font></i>: 
<font color="Maroon" title="c3">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">D</font>
 <b>by </b><i><a class="ref" href="xboole_0.html#D1" target="_self" title="XBOOLE_0:def.1">Def1</a></i>;<br/>
<a NAME="E3:8_1_1"/>
<font color="Maroon" title="c3">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">D</font> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <font color="Maroon" title="c2">X</font>
 
<b>by </b><i><a class="txt" href="xboole_0.html#E2:8_1_1"><i><font color="Green" title="E8">A1</font></i></a>, <a class="ref" href="xboole_0.html#D2" target="_self" title="XBOOLE_0:def.2">Def2</a></i>;<br/>
<a NAME="E4:8_1_1"/><b>then </b>
<font color="Maroon" title="c1">D</font> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <font color="Maroon" title="c2">X</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 
<b>by </b><i><a class="ref" href="xboole_0.html#D1" target="_self" title="XBOOLE_0:def.1">Def1</a></i>;<br/>
<b>hence </b><a NAME="E5:8_1_1"/>
not <font color="Maroon" title="c1">D</font> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <font color="Maroon" title="c2">X</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>
 <b>by </b><i><a class="ref" href="xboole_0.html#D5" target="_self" title="XBOOLE_0:def.5">Def5</a></i>;<br/>


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