torstein

I'm doing some PDE exercices and I'm having a rough time finding out on which variable my problem depends on. For example, if I have to solve the Laplace equation (or any homogeneous PDE) over a cylinder (or sphere) with Dirichlet (or Neumann or Robin) boundary conditions that depends on z and r, how I know if the solution depends on the angular coordinate? What I'm doing actually is set the separation of variables and notice that for the angular part I have not any boundary conditions so I can't find a unique solution. Is that a right way to do that? I know that for the cylinder I have periodical conditions psi(0)=psi(2pi) but it isn't enough right? Anyway, is there a process that let me find out what variables depends on the solution of an homogeneous PDE? Thanks. PS: Sorry for my bad english, isn't my native language.