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<b>let </b><font color="Maroon">d'</font> be    <a href="subset_1.html#M1">Element</a> of  <a href="numbers.html#K5">NAT</a> ;<br/><b>let </b><font color="Maroon">G</font> be    <a href="chain_1.html#M1" target="_self">Grating</a> of <font color="Maroon">d'</font> <a href="nat_1.html#K1">+</a> 1;<br/>



<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="88_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">A</font> be   <a href="chain_1.html#NM3">Cell</a> of <font color="Maroon">d'</font>,<font color="Maroon">G</font>;<br/><a NAME="E1:88_1"/>
<span class="p1">(<span class="default"><a href="chain_1.html#K10" target="_self">star</a> <font color="Maroon">A</font></span>)</span> <a href="subset_1.html#K9">/\</a> <span class="p1">(<span class="default"><a href="chain_1.html#K7" target="_self">Omega</a> <font color="Maroon">G</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="chain_1.html#K10" target="_self">star</a> <font color="Maroon">A</font>
 <b>by </b><i><a class="ref" href="xboole_1.html#T28">XBOOLE_1:28</a></i>;<br/><a NAME="E2:88_1"/><b>then </b>
 <a href="card_1.html#K4">card</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="chain_1.html#K10" target="_self">star</a> <font color="Maroon">A</font></span>)</span> <a href="subset_1.html#K9">/\</a> <span class="p2">(<span class="default"><a href="chain_1.html#K7" target="_self">Omega</a> <font color="Maroon">G</font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a> 2 <a href="nat_1.html#K2">*</a> 1
 <b>by </b><i/>;<br/><b>hence </b><a NAME="E3:88_1"/>
( <font color="Maroon">A</font> <a href="hidden.html#R2">in</a>  <a href="chain_1.html#K11" target="_self">del</a> <span class="p1">(<span class="default"><a href="chain_1.html#K7" target="_self">Omega</a> <font color="Maroon">G</font></span>)</span> iff <font color="Maroon">A</font> <a href="hidden.html#R2">in</a>  <a href="chain_1.html#K6" target="_self">0_</a> <font color="Maroon">d'</font>,<font color="Maroon">G</font> )
 <b>by </b><i/>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E2:88"/>
 <a href="chain_1.html#K11" target="_self">del</a> <span class="p1">(<span class="default"><a href="chain_1.html#K7" target="_self">Omega</a> <font color="Maroon">G</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="chain_1.html#K6" target="_self">0_</a> <font color="Maroon">d'</font>,<font color="Maroon">G</font>
 <b>by </b><i><a class="ref" href="subset_1.html#T8">SUBSET_1:8</a></i>;<br/>


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