(960, #1) Let F(x, y, z) = < 3 x, x y, 2 x z> and E be the cube bounded by the planes x= 0, x = 1, y = 0, y = 1, z = 0, z = 1. Verify that the divergence theorem is true for this case by calculating the two integrals that appear there.


Solution: Computing the integral

appears, at first, to be tedious because it has to be calculated on the 6 different faces of the cube. However, since the faces are parallel to the coordinate planes each of the integrals reduces to the form

where n is the appropriate normal. tabulating the results we have:

Face
Integral
Value
z = 1, x = 0..1, y = 0..1
1
z = 0, x = 0..1, y = 0..1
0
y = 1, x = 0..1, z = 0 ..1
1/2
y = 0, x = 0..1, z = 0..1
0
x = 1, y = 0..1, z = 0..1
3
x = 0, y = 0..1, z = 0..1
0

Consequently,


This agrees with the right side of the divergence theorem equation: