Let $X,Y$ and $Z$ random variables independent and uniformly distributed in $[-1,1]$. Let $R= \sqrt{X^2+Y^2+Z^2}$. Find the density function of $X^2/R^2$, assuming $R^2 \leq 1$.
My attempt: I was trying to find a density function for $X/R$ first but I was unable to find the correct transformation for that purpouse.