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<b>let </b><font color="Maroon">k</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">d</font> be  non <a href="xboole_0.html#V1">zero</a>  <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>;<br/>





<b>assume </b><a NAME="E1:81"/><i><font color="Green">E37</font></i>: 
<font color="Maroon">k</font> <a href="nat_1.html#K1">+</a> 1 <a href="xxreal_0.html#NR4" target="_self">&gt;</a> <font color="Maroon">d</font>
 ;<br/>

<b>let </b><font color="Maroon">C</font> be   <a href="chain_1.html#NM4">Chain</a> of <span class="p1">(<span class="default"><font color="Maroon">k</font> <a href="nat_1.html#K1">+</a> 1</span>)</span>,<font color="Maroon">G</font>;<br/>

<a NAME="E2:81"/>
for <font color="Olive">A</font> being   <a href="hidden.html#M1">set</a>   holds not <font color="Olive">A</font> <a href="hidden.html#R2">in</a>  <a href="chain_1.html#K11" target="_self">del</a> <font color="Maroon">C</font>
 
<b>by </b><i><a class="ref" href="chain_1.html#T4" target="_self">Th4</a>, </i>;<br/>
<a NAME="E3:81"/><b>then </b>
 <a href="chain_1.html#K11" target="_self">del</a> <font color="Maroon">C</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="xboole_0.html#D1">XBOOLE_0:def 1</a></i>;<br/>
<b>hence </b><a NAME="E4:81"/>
 <a href="chain_1.html#K11" target="_self">del</a> <font color="Maroon">C</font> <a href="hidden.html#R1">=</a>  <a href="chain_1.html#K6" target="_self">0_</a> <font color="Maroon">k</font>,<font color="Maroon">G</font>
 ;<br/>


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