Power correct notation Ok, I know this may sound dumb, but I am trying to understand which is the correct (most beauty) notation for the power function ${\rm pow}(f(x),n)$.
This is the correct one: $[f(x)]^n$
From trigonometry, where I was used to write $\cos^2x$, we get: $f^n(x)$
And from Bishop's Pattern Recognition and Machine Learning I get $\mathbb{E}\,[f(x)^2]$, so: $f(x)^n$
So, is there any other 'me' out there who has already found the correct beauty and elegant way?

The trigonometry convention is awful and should never be used, but as the other answer indicates it is fine to use that notation for composition, so $f^2(x) = f(f(x))$ which is consistent with using $f^{-1}$ to denote the inverse of $f$.  The extra parentheses are unnecessary, so just write $f(x)^2$, $\cos(x)^2$, etc.  It is also common to omit all the parentheses in some cases, for example $\cos x$ instead of $\cos(x)$, and I wouldn't be surprised to see $\cos{x^2}$ for $\cos(x^2)$.  
