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<b>let </b><font color="Maroon">R</font> be   <a href="relat_1.html#NM1">Relation</a>;<br/><b>let </b><font color="Maroon">a</font> be    <a href="hidden.html#M1">set</a> , <font color="Maroon">b</font> be    <a href="hidden.html#M1">set</a> ;<br/>



<b>given </b><font color="Maroon">c</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><a NAME="E1:56"/><i><font color="Green">E21</font></i>: 
( ( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">c</font>,<font color="Maroon">a</font></span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <font color="Maroon">R</font> or <font color="Maroon">a</font> <a href="hidden.html#R1">=</a> <font color="Maroon">c</font> ) &amp; ( <span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">c</font>,<font color="Maroon">b</font></span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <font color="Maroon">R</font> or <font color="Maroon">b</font> <a href="hidden.html#R1">=</a> <font color="Maroon">c</font> ) )
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="rewrite1.html#D10" target="_self">REWRITE1:def 10</a><br/>

<b>take </b>
<font color="Maroon">c</font>
; <i><font color="Red">:: according to </font></i><a class="ref" href="rewrite1.html#D8" target="_self">REWRITE1:def 8</a><br/>

<b>thus </b><a NAME="E2:56"/>
( <font color="Maroon">R</font> <a href="rewrite1.html#R1" target="_self">reduces</a> <font color="Maroon">c</font>,<font color="Maroon">a</font> &amp; <font color="Maroon">R</font> <a href="rewrite1.html#R1" target="_self">reduces</a> <font color="Maroon">c</font>,<font color="Maroon">b</font> )
 <b>by </b><i>, , </i>;<br/>


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