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<b>let </b><font color="Maroon">A</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">B</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">A</font>, <font color="Maroon">C</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">A</font>, <font color="Maroon">D</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">A</font>;<br/>



<b>assume </b><a NAME="E1:1"/>
<font color="Maroon">B</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">C</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<a NAME="E2:1"/><b>then </b>
( <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">C</font> &amp; <font color="Maroon">C</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">D</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">C</font> )
 
<b>by </b><i><a class="ref" href="xboole_1.html#T37">XBOOLE_1:37</a>, <a class="ref" href="xboole_1.html#T79">XBOOLE_1:79</a></i>;<br/>
<b>hence </b><a NAME="E3:1"/>
<font color="Maroon">B</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">D</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">C</font>
 <b>by </b><i><a class="ref" href="xboole_1.html#T63">XBOOLE_1:63</a></i>;<br/>


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