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<a NAME="E1:59_1_1"/>
 <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">U1</font>
 
<b>by </b><i><a class="ref" href="classes2.html#T62" target="_self" title="CLASSES2:th.62">Th62</a></i>;<br/>
<b>then reconsider </b><font color="Maroon" title="c2">x</font> =  <a href="zfmisc_1.html#K1" title="ZFMISC_1:func.1">bool</a> <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  as    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Maroon" title="c1">U1</font> <b>by </b><i><a class="ref" href="classes2.html#T65" target="_self" title="CLASSES2:th.65">Th65</a></i>;<br/>
<b>take </b>
<font color="Maroon" title="c2">x</font>
; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> not <font color="Maroon" title="c2">x</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a></span><br/>

<b>thus </b><a NAME="E3:59_1_1"/>
not <font color="Maroon" title="c2">x</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>
 ; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> verum</span><br/>


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