Example 5.  Solve Laplace's equation over the square where the boundary conditions are  
    Top:       180
    Left:         80
    Bottom:   20
    Right:        0

Solution 5.

First set up the boundary values.
,  ,  for  ,  and  ,  for  .

Next, solve it.

Plot the solution by making a table of 3D points and using Mathematica's ListSurfacePlot3D graphics subroutine.  

(c) John H. Mathews 2004