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<b>consider </b><font color="Maroon">x</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E2:8_1_1"/><i><font color="Green">E13</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font>
 <b>by </b><i/>;<br/>
<a NAME="E3:8_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font> <a href="xboole_0.html#K2" target="_self">\/</a> <font color="Maroon">X</font>
 
<b>by </b><i>, </i>;<br/>
<a NAME="E4:8_1_1"/><b>then </b>
<font color="Maroon">D</font> <a href="xboole_0.html#K2" target="_self">\/</a> <font color="Maroon">X</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1" target="_self">{}</a> 
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E5:8_1_1"/>
not <font color="Maroon">D</font> <a href="xboole_0.html#K2" target="_self">\/</a> <font color="Maroon">X</font> is <a href="xboole_0.html#V1" target="_self">empty</a>
 <b>by </b><i/>;<br/>


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