Krull's Height Theorem Proof. http://www2.gsu.edu/~matfxe/commalglectures/lect14.pdf
Here is a proof of Krull's PIT theorem. I don't understand why $\cap_{t\geq 1} (PR_{P})^t = 0$ (written on Page 2, line 3)
If anyone would shed some light that would be great!

It follows from Nakayama's lemma for $M=\bigcap_{t\geq 1} (PR_P)^t$ and $I=PR_P.$ 
