Whichway - you can do calculus? I'm so rusty, it's terrible. I tried to cheat and have Wolfram Alpha compute the indefinite integral. I don't believe it gave the right answer. I'm still ok with derivatives, but double integrals - blah.

Assuming a square sheet centered on the origin, and a point being lit aligned on the z axis, the contribution of any infinitesimal point on that sheet is

1/(x^2+y^2+z^2) where x,y identifies a point on the sheet and z is the distance from the origin of the point being lit.

The attached image shows what needs to be computed. Can you do it?

We actually need the definite integral where x and y go from -.5 to .5.

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