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<b>let </b><font color="Maroon" title="c1">W</font>, <font color="Maroon" title="c2">X</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>



<b>assume </b><a NAME="E1:7"/><i><font color="Green" title="E6">A1</font></i>: 
( <font color="Maroon" title="c1">W</font> <a href="classes1.html#NR1" title="CLASSES1:NR.1">is_Tarski-Class</a>  &amp; <font color="Maroon" title="c2">X</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">W</font> )
 ;<br/>

<b>then reconsider </b><font color="Maroon" title="c3">D</font> = <font color="Maroon" title="c1">W</font> as  non <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>  <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a>  ;<br/>
<a NAME="E3:7"/>
<font color="Maroon" title="c3">D</font> <a href="classes1.html#R1" title="CLASSES1:pred.1">is_Tarski-Class_of</a> <font color="Maroon" title="c2">X</font>
 
<b>by </b><i><a class="txt" href="classes2.html#E1:7"><i><font color="Green" title="E6">A1</font></i></a>, <a class="ref" href="classes1.html#D3" title="CLASSES1:def.3">CLASSES1:def 3</a></i>;<br/>
<b>hence </b><a NAME="E4:7"/>
 <a href="classes1.html#K1" title="CLASSES1:func.1">Tarski-Class</a> <font color="Maroon" title="c2">X</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a> <font color="Maroon" title="c1">W</font>
 <b>by </b><i><a class="ref" href="classes1.html#D4" title="CLASSES1:def.4">CLASSES1:def 4</a></i>;<br/>


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