If r = (x, y, z) and r = norm(r), compute curl [f(r)r], where f is a differentiable function.
I'm confused at what [f(r)r] means. Would I take each partial derivative of r and dot product it with r?
The Key Idea is that is a scalar and is a vector.
This gives in Cartesian coordinates
Now we just need to take the curl so we get
Note that this is using first principles there are product rules for the divergence, gradient, curl ect.
http://en.wikipedia.org/wiki/Vector_...ifferentiation
But you should know how to work them this way as well.