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<b>let </b><font color="Maroon" title="c1">Y</font> be  non <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>  <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/><b>let </b><font color="Maroon" title="c2">a</font> be    <a href="fraenkel.html#M2" title="FRAENKEL:mode.2">Element</a> of  <a href="fraenkel.html#K1" title="FRAENKEL:func.1">Funcs</a> <font color="Maroon" title="c1">Y</font>,<a href="margrel1.html#K6" title="MARGREL1:func.6">BOOLEAN</a> ;<br/>



<font color="Maroon" title="c2">a</font> <a href="bvfunc26.html#K3" title="BVFUNC26:func.3">'nand'</a> <font color="Maroon" title="c2">a</font> = 
 <a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">a</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c2">a</font></span>)</span>
<b>by </b><i><a class="ref" href="bvfunc26.html#T1" target="_self" title="BVFUNC26:th.1">Th1</a></i>
<br/>.= 
 <a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <font color="Maroon" title="c2">a</font>

;<br/>
<b>hence </b><a NAME="E2:10"/>
( <font color="Maroon" title="c2">a</font> <a href="bvfunc26.html#K3" title="BVFUNC26:func.3">'nand'</a> <font color="Maroon" title="c2">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <font color="Maroon" title="c2">a</font> &amp;  <a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">a</font> <a href="bvfunc26.html#K3" title="BVFUNC26:func.3">'nand'</a> <font color="Maroon" title="c2">a</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c2">a</font> )
 ;<br/>


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