1. The problem statement, all variables and given/known data [PLAIN]http://img641.imageshack.us/img641/9458/93563522.jpg [Broken] 2. Relevant equations N/A 3. The attempt at a solution I think the reason I can't solve this problem is possibly I failed to consider some important property of the laplace equation. I just don't have a club where to start. Here's my attempt: "u" is clearly harmonic inside the unit ball. It seems to me that the relationship to be proved suggests a linear interpolation scheme can be used to determine any point inside the ball, which also suggests the divergent everywhere inside the ball is same??? I'm totally confused from here on.