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





<a NAME="E1:31"/>
( <font color="Maroon">A</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">E</font> &amp; <font color="Maroon">B</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">E</font> )
 
<b>by </b><i/>;<br/>
<a NAME="E2:31"/><b>then </b><i><font color="Green">E20</font></i>: 
( <font color="Maroon">A</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">E</font> &amp; <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">E</font> )
 
<b>by </b><i><a class="ref" href="zfmisc_1.html#D1">ZFMISC_1:def 1</a></i>;<br/>
<b>thus </b><span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="subset_1.html#K7" target="_self">\</a> <font color="Maroon">B</font></span>)</span> <a href="subset_1.html#K3" target="_self">`</a>  = 
<span class="p1">(<span class="default"><font color="Maroon">E</font> <a href="subset_1.html#K6" target="_self">\</a> <font color="Maroon">A</font></span>)</span> <a href="subset_1.html#K4" target="_self">\/</a> <span class="p1">(<span class="default"><font color="Maroon">E</font> <a href="subset_1.html#K9" target="_self">/\</a> <font color="Maroon">B</font></span>)</span>
<b>by </b><i><a class="ref" href="xboole_1.html#T52">XBOOLE_1:52</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="subset_1.html#K3" target="_self">`</a> </span>)</span> <a href="subset_1.html#K4" target="_self">\/</a> <font color="Maroon">B</font>
<b>by </b><i>, <a class="ref" href="xboole_1.html#T28">XBOOLE_1:28</a></i>
;<br/>


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