If <i>F</i> is a field of characteristic 0, and <i>a</i> and <i>b</i> are algebraic over <i>F</i>, then there is an element <I>c</i> in 
<I>F</i>(<i>a,b</i>) 
 such that  
<I>F</I>(<i>c</i>) = <I>F</i>(<i>a,b</i>).