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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="funct_2.html#NM1">Function</a> of <font color="Maroon">X</font>,<font color="Maroon">X</font>;<br/>



<b>assume </b><a NAME="E1:74"/><i><font color="Green">E20</font></i>: 
( <font color="Maroon">f</font> is <a href="funct_1.html#V2">one-to-one</a> &amp;  <a href="relset_1.html#K5">rng</a> <font color="Maroon">f</font> <a href="hidden.html#R1">=</a> <font color="Maroon">X</font> )
 ;<br/>

<a NAME="E2:74"/><b>then </b>
<font color="Maroon">f</font> is <a href="funct_2.html#V2" target="_self">onto</a>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:74"/>
<font color="Maroon">f</font> is   <a href="funct_2.html#NM2">Permutation</a> of <font color="Maroon">X</font>
 <b>by </b><i><a class="ref" href="funct_2.html#T4" target="_self">Th4</a>, </i>;<br/>


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