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<b>let </b><font color="Maroon">L</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="orders_2.html#L1">RelStr</a> ;<br/><b>let </b><font color="Maroon">X1</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">L</font>, <font color="Maroon">X2</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">L</font>, <font color="Maroon">Y1</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">L</font>, <font color="Maroon">Y2</font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">L</font>;<br/>



<b>assume </b><a NAME="E1:28"/><i><font color="Green">E20</font></i>: 
( <font color="Maroon">X1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">Y1</font> &amp; <font color="Maroon">X2</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">Y2</font> )
 ;<br/>

<b>let </b><font color="Maroon">q</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E2:28"/>
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X1</font> <a href="yellow_4.html#K1" target="_self">"\/"</a> <font color="Maroon">X2</font>
 ;<br/>

<b>then consider </b><font color="Maroon">x</font> being   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font>, <font color="Maroon">y</font> being   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">L</font><b> such that </b><br/><a NAME="E4:28"/><i><font color="Green">E21</font></i>: 
( <font color="Maroon">q</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x</font> <a href="lattice3.html#K10">"\/"</a> <font color="Maroon">y</font> &amp; <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X1</font> &amp; <font color="Maroon">y</font> <a href="hidden.html#R2">in</a> <font color="Maroon">X2</font> )
 ;<br/>
<b>thus </b><a NAME="E5:28"/>
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Y1</font> <a href="yellow_4.html#K1" target="_self">"\/"</a> <font color="Maroon">Y2</font>
 <b>by </b><i>, </i>;<br/>


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