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<b>let </b><font color="Maroon">f1</font> be   <a href="funct_1.html#NM1">Function</a>, <font color="Maroon">f2</font> be   <a href="funct_1.html#NM1">Function</a>;<br/>

<b>assume </b><b>that </b><br/><a NAME="E1:18_1_2"/><i><font color="Green">E19</font></i>: 
for <font color="Olive">a</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> holds <br/> (  <a href="relat_1.html#K1">dom</a> <font color="Maroon">f1</font> <a href="hidden.html#R1">=</a> the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">L</font> &amp; <font color="Maroon">f1</font> <a href="funct_1.html#K1">.</a> <font color="Olive">a</font> <a href="hidden.html#R1">=</a> <span class="p1">{<span class="default"> <font color="Olive">F</font> where <font color="Olive">F</font> is    <a href="filter_0.html#M1">Filter</a> of <font color="Maroon">L</font> : ( <font color="Olive">F</font> <a href="hidden.html#R2">in</a>  <a href="openlatt.html#K7" target="_self">F_primeSet</a> <font color="Maroon">L</font> &amp; <font color="Olive">a</font> <a href="hidden.html#R2">in</a> <font color="Olive">F</font> ) </span>}</span>  )
 <b>and </b><br/><a NAME="E2:18_1_2"/><i><font color="Green">E40</font></i>: 
for <font color="Olive">a</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> holds <br/> (  <a href="relat_1.html#K1">dom</a> <font color="Maroon">f2</font> <a href="hidden.html#R1">=</a> the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">L</font> &amp; <font color="Maroon">f2</font> <a href="funct_1.html#K1">.</a> <font color="Olive">a</font> <a href="hidden.html#R1">=</a> <span class="p1">{<span class="default"> <font color="Olive">F</font> where <font color="Olive">F</font> is    <a href="filter_0.html#M1">Filter</a> of <font color="Maroon">L</font> : ( <font color="Olive">F</font> <a href="hidden.html#R2">in</a>  <a href="openlatt.html#K7" target="_self">F_primeSet</a> <font color="Maroon">L</font> &amp; <font color="Olive">a</font> <a href="hidden.html#R2">in</a> <font color="Olive">F</font> ) </span>}</span>  )
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="18_1_2_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>assume </b><a NAME="E1:18_1_2_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">L</font>
 ;<br/><b>then reconsider </b><font color="Maroon">a</font> = <font color="Maroon">x</font> as   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> ;<br/><b>thus </b><font color="Maroon">f1</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> = 
<span class="p1">{<span class="default"> <font color="Olive">F</font> where <font color="Olive">F</font> is    <a href="filter_0.html#M1">Filter</a> of <font color="Maroon">L</font> : ( <font color="Olive">F</font> <a href="hidden.html#R2">in</a>  <a href="openlatt.html#K7" target="_self">F_primeSet</a> <font color="Maroon">L</font> &amp; <font color="Maroon">a</font> <a href="hidden.html#R2">in</a> <font color="Olive">F</font> ) </span>}</span> 
<b>by </b><i/>
<br/>.= 
<font color="Maroon">f2</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font>
<b>by </b><i><a class="ref" href="openlatt.html#T1" target="_self">Th1</a></i>
;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E4:18_1_2"/>
<font color="Maroon">f1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">f2</font>
 <b>by </b><i>, <a class="ref" href="openlatt.html#T1" target="_self">Th1</a>, <a class="ref" href="funct_1.html#T9">FUNCT_1:9</a></i>;<br/>


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