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<b>let </b><font color="Maroon">X1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">X2</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">X3</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y2</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y3</font> be    <a href="hidden.html#M1">set</a> ;<br/>











<b>assume </b><a NAME="E1:34"/>
<span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">X1</font>,<font color="Maroon">X2</font>,<font color="Maroon">X3</font></span><a href="zfmisc_1.html#K3">:]</a></span> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<a NAME="E2:34"/><b>then </b>
( <font color="Maroon">X1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">X2</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">X3</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:34"/>
(  not <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">X1</font>,<font color="Maroon">X2</font>,<font color="Maroon">X3</font></span><a href="zfmisc_1.html#K3">:]</a></span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">Y1</font>,<font color="Maroon">Y2</font>,<font color="Maroon">Y3</font></span><a href="zfmisc_1.html#K3">:]</a></span> or ( <font color="Maroon">X1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">Y1</font> &amp; <font color="Maroon">X2</font> <a href="hidden.html#R1">=</a> <font color="Maroon">Y2</font> &amp; <font color="Maroon">X3</font> <a href="hidden.html#R1">=</a> <font color="Maroon">Y3</font> ) )
 <b>by </b><i/>;<br/>


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