# Proving 4 vectors!

In books, it is always posted that velocity (dx$^{i}$/dt) is not a 4 vector. While du$^{i}$/ds and momentum are 4 vectors.. But it is never proved.

How to prove this?? I am not finding anyway to it.

You're my last hope!

Thank you for the reply, but can you tell me which one to use? I mean which formula from the two links?

Simon Bridge
Oh thank you! You mean that if I took the proper time and divided that by ds = cdt $\sqrt{1-(v^2/c^2)}$ I should get the 4 components of U. And I say that yes, these looks like (dA^0, dA^1, dA^2, dA^3) as in your link so it is a 4 vector. Right?