Vector integral question

1. Sep 14, 2010

Melawrghk

1. The problem statement, all variables and given/known data

3. The attempt at a solution
I get parts a and b, but I don't know what to do for part c.
I can write a double integral with dx and dz (because y is constant) and substitute y=7 in, but I'm not sure how to integrate ax...

Any hints would be appreciated.

2. Sep 14, 2010

diazona

First, is ax constant over the integration region? If so, you can pull it out of the integral, just as with a numeric constant.

If it's not constant, you'd need to find a way to express it in terms of things (i.e. other unit vectors) that are constant.

3. Sep 14, 2010

Melawrghk

Well I guess ax is a unit vector in the x direction, so it must be constant.

But how do I figure out the limits of integration for x and z?

4. Sep 14, 2010

diazona

Well, what's the region of integration?

5. Sep 14, 2010

Melawrghk

I don't know, it just says plane y=7.