In cylindrical co-ordinates

\(\frac{1}{\rho }\frac{\partial }{{{\partial _\rho }}}\left( {\rho \frac{{\partial V}}{{{\partial _\rho }}}} \right) + \frac{1}{{{\rho ^2}}}\frac{{{\partial ^2}V}}{{\partial {\phi ^2}}} = 0\) is