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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="E1:95"/><i><font color="Green">E13</font></i>: 
<font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font> <a href="xboole_0.html#R1">misses</a> <font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T51" target="_self">Th51</a></i>;<br/>
<a NAME="E2:95"/>
<font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font></span>)</span>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T50" target="_self">Th50</a></i>;<br/>
<a NAME="E3:95"/><b>then </b><i><font color="Green">E14</font></i>: 
<span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K4">\</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T55" target="_self">Th55</a>, <a class="ref" href="xboole_1.html#T47" target="_self">Th47</a></i>;<br/>
<a NAME="E4:95"/>
<font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K4">\</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font></span>)</span>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T52" target="_self">Th52</a></i>;<br/>
<a NAME="E5:95"/><b>then </b>
<font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T12" target="_self">Th12</a></i>;<br/>
<a NAME="E6:95"/><b>then </b>
<span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K4">\</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="xboole_1.html#T4" target="_self">Th4</a></i>;<br/>
<b>hence </b><a NAME="E7:95"/>
<span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</a> <font color="Maroon">Y</font></span>)</span> <a href="xboole_0.html#K5">\+\</a> <span class="p1">(<span class="default"><font color="Maroon">X</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">Y</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">Y</font>
 <b>by </b><i><a class="txt" href="xboole_1.html#E58"><i><font color="Green">Lemma45</font></i></a></i>;<br/>


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