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<b>let </b><font color="Maroon">z1</font> be    <a href="hidden.html#M1">set</a> , <font color="Maroon">z2</font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>assume </b><a NAME="E1:1_1_2"/>
( ( for <font color="Olive">y1</font>, <font color="Olive">y2</font>, <font color="Olive">y3</font> being   <a href="hidden.html#M1">set</a>   st <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="mcart_1.html#K3">[</a><span class="default"><font color="Olive">y1</font>,<font color="Olive">y2</font>,<font color="Olive">y3</font></span><a href="mcart_1.html#K3">]</a></span> holds <br/><font color="Maroon">z1</font> <a href="hidden.html#R1">=</a> <font color="Olive">y1</font> ) &amp; ( for <font color="Olive">y1</font>, <font color="Olive">y2</font>, <font color="Olive">y3</font> being   <a href="hidden.html#M1">set</a>   st <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="mcart_1.html#K3">[</a><span class="default"><font color="Olive">y1</font>,<font color="Olive">y2</font>,<font color="Olive">y3</font></span><a href="mcart_1.html#K3">]</a></span> holds <br/><font color="Maroon">z2</font> <a href="hidden.html#R1">=</a> <font color="Olive">y1</font> ) )
 ;<br/>

<a NAME="E2:1_1_2"/><b>then </b>
( <font color="Maroon">z1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x1</font> &amp; <font color="Maroon">z2</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x1</font> )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:1_1_2"/>
<font color="Maroon">z1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">z2</font>
 ;<br/>


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