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

<b>assume </b><b>that </b><br/><a NAME="E1:11"/><i><font color="Green">E45</font></i>: 
<font color="Maroon">a</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c</font>
 <b>and </b><br/><a NAME="E2:11"/><i><font color="Green">E57</font></i>: 
<font color="Maroon">b</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c</font> <a href="subset_1.html#K6">\</a> <font color="Maroon">a</font>
 ;<br/>

<b>thus </b><span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <span class="p2">(<span class="default"><font color="Maroon">c</font> <a href="subset_1.html#K6">\</a> <span class="p3">(<span class="default"><font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">b</font></span>)</span></span>)</span></span>)</span> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">b</font> = 
<span class="p1">(<span class="default"><font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <span class="p2">(<span class="default"><span class="p3">(<span class="default"><font color="Maroon">c</font> <a href="subset_1.html#K6">\</a> <font color="Maroon">a</font></span>)</span> <a href="subset_1.html#K7">\</a> <font color="Maroon">b</font></span>)</span></span>)</span> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">b</font>
<b>by </b><i><a class="ref" href="xboole_1.html#T41">XBOOLE_1:41</a></i>
<br/>.= 
<font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><span class="p3">(<span class="default"><font color="Maroon">c</font> <a href="subset_1.html#K6">\</a> <font color="Maroon">a</font></span>)</span> <a href="subset_1.html#K7">\</a> <font color="Maroon">b</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">b</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T4">XBOOLE_1:4</a></i>
<br/>.= 
<font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c</font> <a href="subset_1.html#K6">\</a> <font color="Maroon">a</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">b</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T39">XBOOLE_1:39</a></i>
<br/>.= 
<font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><font color="Maroon">c</font> <a href="subset_1.html#K6">\</a> <font color="Maroon">a</font></span>)</span>
<b>by </b><i>, <a class="ref" href="xboole_1.html#T12">XBOOLE_1:12</a></i>
<br/>.= 
<font color="Maroon">a</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">c</font>
<b>by </b><i><a class="ref" href="xboole_1.html#T39">XBOOLE_1:39</a></i>
<br/>.= 
<font color="Maroon">c</font>
<b>by </b><i>, <a class="ref" href="xboole_1.html#T12">XBOOLE_1:12</a></i>
;<br/>


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