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<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y</font> be    <a href="hidden.html#M1">set</a> ;<br/>



<a NAME="E1:92"/>
( <font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">X</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font> &amp; <font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">Y</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">X</font> )
 
<b>by </b><i><a class="ref" href="xboole_1.html#T49" target="_self">Th49</a></i>;<br/>
<a NAME="E2:92"/><b>then </b>
<font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font> <a href="xboole_0.html#R1">misses</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><font color="Maroon">Y</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">X</font></span>)</span>
 
<b>by </b><i><a class="txt" href="xboole_1.html#E36"><i><font color="Green">Lemma34</font></i></a></i>;<br/>
<b>hence </b><a NAME="E3:92"/>
<font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font>
 ;<br/>


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