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<b>let </b><font color="Maroon">L</font> be   <a href="lattices.html#NM2">D_Lattice</a>;<br/><b>let </b><font color="Maroon">x1</font> be    <a href="hidden.html#M1">set</a> , <font color="Maroon">x2</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="funct_1.html#D8">FUNCT_1:def 8</a><br/>



<b>assume </b><b>that </b><br/><a NAME="E1:36"/><i><font color="Green">E18</font></i>: 
( <font color="Maroon">x1</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><a href="openlatt.html#K8" target="_self">StoneH</a> <font color="Maroon">L</font></span>)</span> &amp; <font color="Maroon">x2</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><a href="openlatt.html#K8" target="_self">StoneH</a> <font color="Maroon">L</font></span>)</span> )
 <b>and </b><br/><a NAME="E2:36"/><i><font color="Green">E19</font></i>: 
<span class="p1">(<span class="default"><a href="openlatt.html#K8" target="_self">StoneH</a> <font color="Maroon">L</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x1</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="openlatt.html#K8" target="_self">StoneH</a> <font color="Maroon">L</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x2</font>
 ;<br/>

<b>reconsider </b><font color="Maroon">a1</font> = <font color="Maroon">x1</font>, <font color="Maroon">a2</font> = <font color="Maroon">x2</font> as   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font> <b>by </b><i>, </i>;<br/>
<a NAME="E4:36"/>
<font color="Maroon">a1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">a2</font>
 
<b>by </b><i><a class="ref" href="openlatt.html#D3" target="_self">Def3</a>, </i>;<br/>
<b>hence </b><a NAME="E5:36"/>
<font color="Maroon">x1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x2</font>
 ;<br/>


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