I am trying to numerically calculate the electric potential inside a truncated cone using the finite element method (FEM). The cone is embedded in cylindrical coordinates (r,phi,z). I am assuming phi-independence on the potential, therefore the problem is essentially 2D; I am working only with coordinates (r,z). I know how to do FEM in 2D using cartesian coordinates. Do any of you know how to do FEM in 3D using cylindrical coordinates; with a domain that is essentially 2D?