Can someone clue me in to the meaning of $f^2$ in the following:
$f(x^2+y^2)=f^2(x)+f^2(y)$
Does this mean the same as $f(x^2+y^2)=f(x)^2+f(y)^2$
or maybe
$f(x^2+y^2)=f(f(x))+f(f(y))$
?
god i hope i got the $\latex$ right