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<b>let </b><font color="Maroon">i</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="pboole.html#D16">PBOOLE:def 16</a><br/>

<b>assume </b><a NAME="E1:58_1_1"/>
<font color="Maroon">i</font> <a href="hidden.html#R2">in</a> the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">S</font>
 ;<br/>

<b>then reconsider </b><font color="Maroon">s</font> = <font color="Maroon">i</font> as   <a href="msualg_1.html#NM1">SortSymbol</a> of <font color="Maroon">S</font> ;<br/>
<b>consider </b><font color="Maroon">x</font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">R</font> <a href="msualg_4.html#K1">.</a> <font color="Maroon">s</font>;<br/>
<a NAME="E4:58_1_1"/>
<font color="Maroon">R</font> <a href="pboole.html#R2">c=</a>  <a href="msualg_6.html#K6" target="_self">InvCl</a> <font color="Maroon">R</font>
 
<b>by </b><i/>;<br/>
<a NAME="E5:58_1_1"/><b>then </b>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">R</font> <a href="msualg_4.html#K1">.</a> <font color="Maroon">s</font> &amp; <font color="Maroon">R</font> <a href="msualg_4.html#K1">.</a> <font color="Maroon">s</font> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="msualg_6.html#K6" target="_self">InvCl</a> <font color="Maroon">R</font></span>)</span> <a href="msualg_4.html#K1">.</a> <font color="Maroon">s</font> )
 
<b>by </b><i><a class="ref" href="pboole.html#D5">PBOOLE:def 5</a></i>;<br/>
<b>hence </b><a NAME="E6:58_1_1"/>
not <span class="p1">(<span class="default"><a href="msualg_6.html#K6" target="_self">InvCl</a> <font color="Maroon">R</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/>


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