r(t) is the position of a particle in space at time t. Find the angle between the velocity and and acceleration vectors at time t=0.

$\displaystyle r(t)=(3t+1)i+(\sqrt{3})tj+t^{2}k,$

I can find the velocity and acceleration vectors easily. I just don't know how to find the angle between the vectors. Any help?

Nevermind, I found it.

$\displaystyle \theta = cos^{-1}(\frac{u\cdot v}{|u||v|})$