NAME:
evaluatephiforces
PURPOSE:
convenience function to evaluate a possible sum of potentials
R - cylindrical Galactocentric distance
z - distance above the plane
Pot - a potential or list of potentials
phi - azimuth (optional)
t - time (optional)
OUTPUT:
F_phi(R,z,phi,t)
HISTORY:
2010-04-16 - Written - Bovy (NYU)