Solution
= Solution
Differentiate the <cumulative distribution function> using the <chain rule>:
$$
\boxed{f(y)=F'(y)=\frac1{\pi x_0}\frac1{1+(y/x_0)^2}=\frac{x_0}{\pi(x_0^2+y^2)}.}
$$
This is a <Cauchy distribution> with location zero and scale $x_0$. The <probability density function> is nonnegative and integrates to $F(\infty)-F(-\infty)=1$.