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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> ;<br/>



<b>assume </b><a NAME="E1:58"/>
not <font color="Maroon">a</font> <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K3">field</a> <font color="Maroon">R</font>
 ;<br/>

<a NAME="E2:58"/><b>then </b>
<font color="Maroon">a</font> <a href="rewrite1.html#R4" target="_self">is_a_normal_form_of</a> <font color="Maroon">a</font>,<font color="Maroon">R</font>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:58"/>
 ex <font color="Olive">b</font> being   <a href="hidden.html#M1">set</a>  st <font color="Olive">b</font> <a href="rewrite1.html#R4" target="_self">is_a_normal_form_of</a> <font color="Maroon">a</font>,<font color="Maroon">R</font>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="rewrite1.html#D11" target="_self">REWRITE1:def 11</a><br/>


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