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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/>



<i><font color="Green">E13</font></i>: <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> <a href="xboole_0.html#K4">\</a> <font color="Maroon">X</font> = 
<font color="Maroon">Y</font> <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">X</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T16" target="_self">Th16</a></i>
<br/>.= 
<font color="Maroon">Y</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">X</font>

;<br/>
<a NAME="E2:96"/><i><font color="Green">E14</font></i>: 
<font color="Maroon">X</font> <a href="xboole_0.html#K4">\</a> <font color="Maroon">Y</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">X</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T12" target="_self">Th12</a></i>;<br/>
<font color="Maroon">X</font> <a href="xboole_0.html#K4">\</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> = 
<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">X</font> <a href="xboole_0.html#K3">/\</a> <font color="Maroon">X</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T26" target="_self">Th26</a></i>
<br/>.= 
<font color="Maroon">X</font>
<b>by </b><i><a class="txt" href="xboole_1.html#E58"><i><font color="Green">Lemma45</font></i></a>, </i>
;<br/>
<b>hence </b><a NAME="E4:96"/>
<font color="Maroon">X</font> <a href="xboole_0.html#K5">\+\</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> <a href="hidden.html#R1">=</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#T55" target="_self">Th55</a>, </i>;<br/>


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