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<b>let </b><font color="Maroon">D</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">RD</font> be   <a href="eqrel_1.html#NM2">Equivalence_Relation</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">a</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">b</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">F</font> be    <a href="filter_1.html#M2" target="_self">BinOp</a> of <font color="Maroon">D</font>,<font color="Maroon">RD</font>;<br/>









<a NAME="E1:8"/>
( <font color="Maroon">a</font> <a href="hidden.html#R2">in</a>  <a href="eqrel_1.html#K10">EqClass</a> <font color="Maroon">RD</font>,<font color="Maroon">a</font> &amp; <font color="Maroon">b</font> <a href="hidden.html#R2">in</a>  <a href="eqrel_1.html#K10">EqClass</a> <font color="Maroon">RD</font>,<font color="Maroon">b</font> )
 
<b>by </b><i><a class="ref" href="eqrel_1.html#T28">EQREL_1:28</a></i>;<br/>
<b>hence </b><a NAME="E2:8"/>
<span class="p1">(<span class="default"><font color="Maroon">F</font> <a href="filter_1.html#K3" target="_self">/\/</a> <font color="Maroon">RD</font></span>)</span> <a href="binop_1.html#K1">.</a> <span class="p1">(<span class="default"><a href="eqrel_1.html#K7">Class</a> <font color="Maroon">RD</font>,<font color="Maroon">a</font></span>)</span>,<span class="p1">(<span class="default"><a href="eqrel_1.html#K7">Class</a> <font color="Maroon">RD</font>,<font color="Maroon">b</font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="eqrel_1.html#K7">Class</a> <font color="Maroon">RD</font>,<span class="p1">(<span class="default"><font color="Maroon">F</font> <a href="binop_1.html#K2">.</a> <font color="Maroon">a</font>,<font color="Maroon">b</font></span>)</span>
 <b>by </b><i/>;<br/>


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