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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">A1</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">X1</font>;<br/><b>let </b><font color="Maroon">A2</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">X2</font>;<br/><b>let </b><font color="Maroon">A3</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">X3</font>;<br/><b>let </b><font color="Maroon">x</font> be    <a href="subset_1.html#M1">Element</a> of <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>;<br/>













<b>assume </b><a NAME="E1:73"/><i><font color="Green">E39</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A1</font>,<font color="Maroon">A2</font>,<font color="Maroon">A3</font></span><a href="zfmisc_1.html#K3">:]</a></span>
 ;<br/>

<a NAME="E2:73"/><b>then </b><i><font color="Green">E40</font></i>: 
( <font color="Maroon">A1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">A2</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">A3</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a>  )
 
<b>by </b><i/>;<br/>
<b>reconsider </b><font color="Maroon">y</font> = <font color="Maroon">x</font> as    <a href="subset_1.html#M1">Element</a> of <span class="p1"><a href="zfmisc_1.html#K3">[:</a><span class="default"><font color="Maroon">A1</font>,<font color="Maroon">A2</font>,<font color="Maroon">A3</font></span><a href="zfmisc_1.html#K3">:]</a></span> <b>by </b><i/>;<br/>
<a NAME="E4:73"/>
( <font color="Maroon">y</font> <a href="mcart_1.html#K5" target="_self">`1</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A1</font> &amp; <font color="Maroon">y</font> <a href="mcart_1.html#K6" target="_self">`2</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A2</font> &amp; <font color="Maroon">y</font> <a href="mcart_1.html#K7" target="_self">`3</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A3</font> )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E5:73"/>
( <font color="Maroon">x</font> <a href="mcart_1.html#K5" target="_self">`1</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A1</font> &amp; <font color="Maroon">x</font> <a href="mcart_1.html#K6" target="_self">`2</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A2</font> &amp; <font color="Maroon">x</font> <a href="mcart_1.html#K7" target="_self">`3</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">A3</font> )
 <b>by </b><i/>;<br/>


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