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

<a NAME="E1:6"/>
( ( (  <a href="gate_1.html#NR1" target="_self">$</a> <font color="Maroon">a</font> &amp; not  <a href="gate_1.html#NR1" target="_self">$</a> <font color="Maroon">a</font> ) or ( not  <a href="gate_1.html#NR1" target="_self">$</a> <font color="Maroon">a</font> &amp;  <a href="gate_1.html#NR1" target="_self">$</a> <font color="Maroon">a</font> ) ) iff  <a href="gate_1.html#NR1" target="_self">$</a>  <a href="gate_1.html#K4" target="_self">XOR2</a> <font color="Maroon">a</font>,<font color="Maroon">a</font> )
 
<b>by </b><i><a class="ref" href="gate_1.html#D1" target="_self">Def1</a></i>;<br/>
<b>hence </b><a NAME="E2:6"/>
not  <a href="gate_1.html#NR1" target="_self">$</a>  <a href="gate_1.html#K4" target="_self">XOR2</a> <font color="Maroon">a</font>,<font color="Maroon">a</font>
 ;<br/>


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