Hey I have been given the below question but am really struggling to get even the first part:

We want to find the value of the electrostatic potential

in the quadrant.

,

where

and

are the standard polar co-ordinates and

is a given positive real number. Assuming electrostatic potential is the solution of Laplaces equation in polar co-ordinates

The boundary conditions on

are

(a) State why the differential equation with the given boundary conditions can't be solved by the method of separating variables.

The problem I am having is that I can separate the equation into to parts so I am assuming it is to do with the boundary conditions why it cannot be solved, but I don't know what aspect of the conditions effects this?