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<b>let </b><font color="Maroon" title="c1">A</font>, <font color="Maroon" title="c2">B</font>, <font color="Maroon" title="c3">C</font>, <font color="Maroon" title="c4">D</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>

<b>assume </b><a NAME="E1:110"/>
( <font color="Maroon" title="c1">A</font> <a href="xboole_0.html#R1" title="XBOOLE_0:pred.1">misses</a> <font color="Maroon" title="c4">D</font> &amp; <font color="Maroon" title="c2">B</font> <a href="xboole_0.html#R1" title="XBOOLE_0:pred.1">misses</a> <font color="Maroon" title="c4">D</font> )
 ;<br/>

<a NAME="E2:110"/><b>then </b><i><font color="Green" title="E47">A1</font></i>: 
<font color="Maroon" title="c1">A</font> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <font color="Maroon" title="c2">B</font> <a href="xboole_0.html#R1" title="XBOOLE_0:pred.1">misses</a> <font color="Maroon" title="c4">D</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T70" target="_self" title="XBOOLE_1:th.70">Th70</a></i>;<br/>
<b>assume </b><a NAME="E3:110"/>
<font color="Maroon" title="c3">C</font> <a href="xboole_0.html#R1" title="XBOOLE_0:pred.1">misses</a> <font color="Maroon" title="c4">D</font>
 ;<br/>

<b>hence </b><a NAME="E4:110"/>
<span class="p1">(<span class="default"><font color="Maroon" title="c1">A</font> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <font color="Maroon" title="c2">B</font></span>)</span> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <font color="Maroon" title="c3">C</font> <a href="xboole_0.html#R1" title="XBOOLE_0:pred.1">misses</a> <font color="Maroon" title="c4">D</font>
 <b>by </b><i><a class="txt" href="xboole_1.html#E2:110"><i><font color="Green" title="E47">A1</font></i></a>, <a class="ref" href="xboole_1.html#T70" target="_self" title="XBOOLE_1:th.70">Th70</a></i>;<br/>


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