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<b>take </b>
 <a href="pre_topc.html#K2">[#]</a> <font color="Maroon">L</font>
;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="15_1_1_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">x</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>;<br/><b>assume </b><a NAME="E1:15_1_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a>  <a href="pre_topc.html#K2">[#]</a> <font color="Maroon">L</font>
 ;<br/><a NAME="E2:15_1_1_1"/>
 <a href="yellow_0.html#K3">Bottom</a> <font color="Maroon">L</font> <a href="waybel_3.html#NR2" target="_self">&lt;&lt;</a> <font color="Maroon">x</font>
 <b>by </b><i><a class="ref" href="waybel_3.html#T4">WAYBEL_3:4</a></i>;<br/><b>hence </b><a NAME="E3:15_1_1_1"/>
 ex <font color="Olive">y</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> st <br/>( <font color="Olive">y</font> <a href="hidden.html#R2">in</a>  <a href="pre_topc.html#K2">[#]</a> <font color="Maroon">L</font> &amp; <font color="Olive">y</font> <a href="waybel_3.html#NR2" target="_self">&lt;&lt;</a> <font color="Maroon">x</font> )
 ;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E2:15_1_1"/>
 <a href="pre_topc.html#K2">[#]</a> <font color="Maroon">L</font> is <a href="waybel_6.html#V1" target="_self">Open</a>
 <b>by </b><i/>;<br/>


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