Assume that
$T(n) = 2T\left(\frac{n}{2}\right) + \Theta(n \log n)$
By Generic form of master theorem with $a = 2$, $b = 2$ and $f(n) = c \, n \log n$, it can easily be proved that $T(n) = \Theta(n \log^2 n)$.
Though I am not able to understand how exactly does this derive from the master thoerem. Is there any way we can prove the generic form using the original form?