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<b>consider </b><font color="Maroon">x</font> being  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">F</font>;<br/>
<b>take </b><font color="Maroon">v</font> = <span class="p1"><a href="finseq_1.html#K12">&lt;*</a><span class="default"><font color="Maroon">x</font></span><a href="finseq_1.html#K12">*&gt;</a></span>;<br/>

<b>thus </b><a NAME="E2:4_1_1"/>
not <font color="Maroon">v</font> is <a href="xboole_0.html#V1">empty</a>
 ;<br/>

<a NAME="E3:4_1_1"/>
 <a href="relat_1.html#K2">rng</a> <font color="Maroon">v</font> <a href="hidden.html#R1">=</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">x</font></span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i><a class="ref" href="finseq_1.html#T56">FINSEQ_1:56</a></i>;<br/>
<a NAME="E4:4_1_1"/><b>then </b>
not  <a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K2">rng</a> <font color="Maroon">v</font>
 
<b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<b>hence </b><a NAME="E5:4_1_1"/>
<font color="Maroon">v</font> is <a href="relat_1.html#V2">non-empty</a>
 <b>by </b><i><a class="ref" href="relat_1.html#D9">RELAT_1:def 9</a></i>;<br/>


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