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<b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">F</font> be   <a href="armstrng.html#NM2">Dependency-set</a> of <font color="Maroon">X</font>;<br/>



<b>assume </b><a NAME="E1:62"/>
( <font color="Maroon">F</font> is <a href="armstrng.html#V7" target="_self">(DC3)</a> &amp; <font color="Maroon">F</font> is <a href="relat_2.html#V8">(F2)</a> )
 ;<br/>

<b>then reconsider </b><font color="Maroon">F'</font> = <font color="Maroon">F</font> as  <a href="relat_2.html#V8">(F2)</a> <a href="armstrng.html#V7" target="_self">(DC3)</a> <a href="armstrng.html#NM2">Dependency-set</a> of <font color="Maroon">X</font> ;<br/>
<a NAME="E3:62"/>
<font color="Maroon">F'</font> <a href="hidden.html#R1">=</a> <font color="Maroon">F</font>
 
;<br/>
<b>hence </b><a NAME="E4:62"/>
( <font color="Maroon">F</font> is <a href="armstrng.html#V3" target="_self">(F1)</a> &amp; <font color="Maroon">F</font> is <a href="armstrng.html#V4" target="_self">(F3)</a> )
 ;<br/>


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