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<b>let </b><font color="Maroon">S</font> be    <a href="struct_0.html#L1">1-sorted</a> ;<br/>

<b>assume </b><a NAME="E1:7_1_1"/>
not <font color="Maroon">S</font> is <a href="realset2.html#V3">trivial</a>
 ;<br/>

<b>then reconsider </b><font color="Maroon">A</font> = the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">S</font> as  non <a href="realset1.html#V1">trivial</a>  <a href="hidden.html#M1">set</a>  <b>by </b><i><a class="ref" href="realset2.html#D5">REALSET2:def 5</a></i>;<br/>
<a NAME="E3:7_1_1"/>
not <font color="Maroon">A</font> is <a href="xboole_0.html#V1">empty</a>
 
;<br/>
<b>hence </b><a NAME="E4:7_1_1"/>
not <font color="Maroon">S</font> is <a href="struct_0.html#V3">empty</a>
 <b>by </b><i><a class="ref" href="struct_0.html#D1">STRUCT_0:def 1</a></i>;<br/>


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