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<b>let </b><font color="Maroon">X</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Y</font> be  non <a href="xboole_0.html#V1">empty</a>  <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">Y</font>;<br/><b>let </b><font color="Maroon">g</font> be   <a href="funct_2.html#NM1">Function</a> of <font color="Maroon">Y</font>,<font color="Maroon">X</font>;<br/>







<b>assume </b><a NAME="E1:17"/>
( <font color="Maroon">f</font> is <a href="funct_1.html#V2">one-to-one</a> &amp; <font color="Maroon">g</font> is <a href="funct_1.html#V2">one-to-one</a> )
 ;<br/>

<a NAME="E2:17"/><b>then </b>
 ex <font color="Olive">h</font> being  <a href="funct_2.html#NM1">Function</a> of <font color="Maroon">X</font>,<font color="Maroon">Y</font> st <font color="Olive">h</font> is <a href="funct_2.html#V3">bijective</a>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:17"/>
<font color="Maroon">X</font>,<font color="Maroon">Y</font> <a href="tarski.html#R2">are_equipotent</a> 
 <b>by </b><i/>;<br/>


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