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<b>take </b>
 <a href="xboole_0.html#K1">{}</a> 
;<br/>

<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="funct_1.html#D15" target="_self">FUNCT_1:def 15</a><br/>

<b>thus </b><a NAME="E1:112_1_1"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <a href="xboole_0.html#K1">{}</a>  implies  not <a href="xboole_0.html#K1">{}</a>  <a href="funct_1.html#K1" target="_self">.</a> <font color="Maroon">x</font> is <a href="xboole_0.html#V1">empty</a> )
 ;<br/>


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