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<b>consider </b><font color="Maroon">a0</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E2:1_1"/><i><font color="Green">E30</font></i>: 
<font color="Maroon">a0</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F<sub>1</sub></font>()
 <b>by </b><i><a class="ref" href="xboole_0.html#D1">XBOOLE_0:def 1</a></i>;<br/>
<a NAME="E3:1_1"/>
<font color="Maroon">F<sub>2</sub></font>(<font color="Maroon">a0</font>) <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <font color="Maroon">F<sub>2</sub></font>(<font color="Olive">a</font>) where <font color="Olive">a</font> is    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">F<sub>1</sub></font>() : verum </span>}</span> 
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E4:1_1"/>
not <span class="p1">{<span class="default"> <font color="Maroon">F<sub>2</sub></font>(<font color="Olive">a</font>) where <font color="Olive">a</font> is    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">F<sub>1</sub></font>() : verum </span>}</span>  is <a href="xboole_0.html#V1">empty</a>
 ;<br/>


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