Vector identity

[Kolahal Bhattacharya]

Homework Statement

I am to show: closed integral {phi (grad phi)} X (n^)dS=0

Homework Equations

The Attempt at a Solution

I understand I am to use divergence theorem here.but cannot approach.Please help

 

[Dick]

Is 'X' supposed to mean a cross product between the normal vector and the gradient?

 

[Kolahal Bhattacharya]

yes.It means that.

 

[Dick]

Try using $$\int_S n \times a dS = \int_V curl(a) dV$$.