# Flux through a box? And divergence as a limit?

1. Feb 23, 2012

Let F=(7z+8)i+2zj+(2z+7)k, and let the point P=(abc), where a, b and c are constants. In this problem we will calculate div F in two different ways, first by using the geometric definition and second by using partial derivatives.

(a) Consider a (three-dimensional) box with four of its corners at (abc), (a+wbc), (ab+wc) and (abc+w), where w is a constant edge length. Find the flux through the box.

Thus, we have
div F(xyz)=lim/(w->0) = (BLANK/BLANK) = 2

I solved the div F to be 2... don't know how to solve for flux or the lim.

the lim in the text book is written as lim ϵ-> 0 (3/4piϵ**3) o∫∫[F.NdS]

thanks for the help!

2. Feb 23, 2012