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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> ;<br/>

<a NAME="E1:22"/>
( <font color="Maroon">A</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">B</font> &amp; <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">B</font> )
 
<b>by </b><i><a class="ref" href="xboole_1.html#T7">XBOOLE_1:7</a></i>;<br/>
<a NAME="E2:22"/><b>then </b>
(  <a href="finsub_1.html#K5" target="_self">Fin</a> <font color="Maroon">A</font> <a href="tarski.html#R1">c=</a>  <a href="finsub_1.html#K5" target="_self">Fin</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">B</font></span>)</span> &amp;  <a href="finsub_1.html#K5" target="_self">Fin</a> <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a>  <a href="finsub_1.html#K5" target="_self">Fin</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">B</font></span>)</span> )
 
<b>by </b><i><a class="ref" href="finsub_1.html#D4" target="_self">Def4</a></i>;<br/>
<b>hence </b><a NAME="E3:22"/>
<span class="p1">(<span class="default"><a href="finsub_1.html#K5" target="_self">Fin</a> <font color="Maroon">A</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><a href="finsub_1.html#K5" target="_self">Fin</a> <font color="Maroon">B</font></span>)</span> <a href="tarski.html#R1">c=</a>  <a href="finsub_1.html#K5" target="_self">Fin</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <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#T8">XBOOLE_1:8</a></i>;<br/>


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