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<b>let </b><font color="Maroon">C</font> be    <a href="altcat_1.html#L2" target="_self">AltCatStr</a> ;<br/>

<b>assume </b><a NAME="E1:56_1_1"/><i><font color="Green">E15</font></i>: 
( <font color="Maroon">C</font> is <a href="realset2.html#V3">trivial</a> &amp; not <font color="Maroon">C</font> is <a href="struct_0.html#V3">empty</a> )
 ;<br/>

<b>let </b><font color="Maroon">i</font> be   <a href="altcat_1.html#NM1">object</a> of <font color="Maroon">C</font>, <font color="Maroon">j</font> be   <a href="altcat_1.html#NM1">object</a> of <font color="Maroon">C</font>; <i><font color="Red">:: according to </font></i><a class="ref" href="altcat_1.html#D20" target="_self">ALTCAT_1:def 20</a><br/>

<b>assume </b><a NAME="E2:56_1_1"/>
<span class="p1"><a href="altcat_1.html#K1" target="_self">&lt;^</a><span class="default"><font color="Maroon">i</font>,<font color="Maroon">j</font></span><a href="altcat_1.html#K1" target="_self">^&gt;</a></span> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<b>thus </b><a NAME="E3:56_1_1"/>
<font color="Maroon">i</font> <a href="hidden.html#R1">=</a> <font color="Maroon">j</font>
 <b>by </b><i>, <a class="ref" href="realset2.html#D7">REALSET2:def 7</a></i>;<br/>


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