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<b>let </b><font color="Maroon">A</font> be    <a href="hidden.html#M1">set</a> ;<br/><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">a</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">D</font>;<br/><b>let </b><font color="Maroon">o</font> be   <a href="binop_1.html#NM2">BinOp</a> of <font color="Maroon">D</font>;<br/>







<b>assume </b><a NAME="E1:20"/><i><font color="Green">E43</font></i>: 
<font color="Maroon">a</font> <a href="binop_1.html#R3">is_a_unity_wrt</a> <font color="Maroon">o</font>
 ;<br/>

<b>set </b><font color="Maroon">e</font> = <font color="Maroon">A</font> <a href="monoid_1.html#K5" target="_self">--&gt;</a> <font color="Maroon">a</font>;<br/>
<b>set </b><font color="Maroon">F</font> = <font color="Maroon">o</font>,<font color="Maroon">D</font> <a href="monoid_1.html#K8" target="_self">.:</a> <font color="Maroon">A</font>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="20_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">f</font> be    <a href="fraenkel.html#M2">Element</a> of  <a href="fraenkel.html#K1">Funcs</a> <font color="Maroon">A</font>,<font color="Maroon">D</font>;<br/><a NAME="E1:20_1"/><i><font color="Green">E44</font></i>: 
 <a href="relset_1.html#K4">dom</a> <font color="Maroon">f</font> <a href="hidden.html#R1">=</a> <font color="Maroon">A</font>
 <b>by </b><i><a class="ref" href="funct_2.html#D1">FUNCT_2:def 1</a></i>;<br/><b>thus </b><span class="p1">(<span class="default"><font color="Maroon">o</font>,<font color="Maroon">D</font> <a href="monoid_1.html#K8" target="_self">.:</a> <font color="Maroon">A</font></span>)</span> <a href="binop_1.html#K2">.</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="monoid_1.html#K5" target="_self">--&gt;</a> <font color="Maroon">a</font></span>)</span>,<font color="Maroon">f</font> = 
<font color="Maroon">o</font> <a href="monoid_1.html#K3" target="_self">.:</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="monoid_1.html#K5" target="_self">--&gt;</a> <font color="Maroon">a</font></span>)</span>,<font color="Maroon">f</font>
<b>by </b><i/>
<br/>.= 
<font color="Maroon">o</font> <a href="monoid_1.html#K6" target="_self">[;]</a> <font color="Maroon">a</font>,<font color="Maroon">f</font>
<b>by </b><i>, <a class="ref" href="funcop_1.html#T41">FUNCOP_1:41</a></i>
<br/>.= 
<font color="Maroon">f</font>
<b>by </b><i>, </i>
;<br/><b>thus </b><span class="p1">(<span class="default"><font color="Maroon">o</font>,<font color="Maroon">D</font> <a href="monoid_1.html#K8" target="_self">.:</a> <font color="Maroon">A</font></span>)</span> <a href="binop_1.html#K2">.</a> <font color="Maroon">f</font>,<span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="monoid_1.html#K5" target="_self">--&gt;</a> <font color="Maroon">a</font></span>)</span> = 
<font color="Maroon">o</font> <a href="monoid_1.html#K3" target="_self">.:</a> <font color="Maroon">f</font>,<span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="monoid_1.html#K5" target="_self">--&gt;</a> <font color="Maroon">a</font></span>)</span>
<b>by </b><i/>
<br/>.= 
<font color="Maroon">o</font> <a href="monoid_1.html#K7" target="_self">[:]</a> <font color="Maroon">f</font>,<font color="Maroon">a</font>
<b>by </b><i>, <a class="ref" href="funcop_1.html#T34">FUNCOP_1:34</a></i>
<br/>.= 
<font color="Maroon">f</font>
<b>by </b><i>, </i>
;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E3:20"/>
<font color="Maroon">A</font> <a href="monoid_1.html#K5" target="_self">--&gt;</a> <font color="Maroon">a</font> <a href="binop_1.html#R3">is_a_unity_wrt</a> <font color="Maroon">o</font>,<font color="Maroon">D</font> <a href="monoid_1.html#K8" target="_self">.:</a> <font color="Maroon">A</font>
 <b>by </b><i><a class="ref" href="binop_1.html#T11">BINOP_1:11</a></i>;<br/>


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