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<b>let </b><font color="Maroon">X</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x0</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">A</font> be  non <a href="xboole_0.html#V1">empty</a> <a href="struct_0.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">x0</font> <a href="topgen_3.html#K6" target="_self">-PointClTop</a> <font color="Maroon">X</font></span>)</span>;<br/>





<b>thus </b> <a href="pre_topc.html#K4">Cl</a> <font color="Maroon">A</font> = 
 <a href="cqc_lang.html#K1">IFEQ</a> <font color="Maroon">A</font>,<a href="arytm_3.html#K13">{}</a> ,<font color="Maroon">A</font>,<span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <span class="p2">(<span class="default"><span class="p3"><a href="domain_1.html#K6">{</a><span class="default"><font color="Maroon">x0</font></span><a href="domain_1.html#K6">}</a></span> <a href="subset_1.html#K8">/\</a> <font color="Maroon">X</font></span>)</span></span>)</span>
<b>by </b><i/>
<br/>.= 
<font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><span class="p2"><a href="domain_1.html#K6">{</a><span class="default"><font color="Maroon">x0</font></span><a href="domain_1.html#K6">}</a></span> <a href="subset_1.html#K8">/\</a> <font color="Maroon">X</font></span>)</span>
<b>by </b><i><a class="ref" href="cqc_lang.html#D1">CQC_LANG:def 1</a></i>
<br/>.= 
<font color="Maroon">A</font> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="domain_1.html#K6">{</a><span class="default"><font color="Maroon">x0</font></span><a href="domain_1.html#K6">}</a></span>
<b>by </b><i><a class="ref" href="xboole_1.html#T28">XBOOLE_1:28</a></i>
;<br/>


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