# I do not understand this vector identity proof

1. Oct 17, 2011

### Xyius

So I am trying to follow my professors notes. Here is my work on the proof. And on the bottom is my answer and his answer. I know my answer is wrong, as I do not fully understand how to convert the summations at the end to their vector quantities. Is my work incorrect?

[PLAIN]http://img256.imageshack.us/img256/6175/questionn.gif [Broken]

I do not even know what F times nabla means. I know nabla times F is divergence. Are they the same????

EDIT: Oh and his G is my q.

AND his answer has a -(G*Nabla)*F at the end.

Last edited by a moderator: May 5, 2017
2. Oct 23, 2011

### pari777

u know, i have done the above proof, i.e,
curl of (A χ B)
but it came out to be (B .$\nabla$)A-B($\nabla$ . A)-(A.$\nabla$) B+ A ($\nabla$ . B)

u see, i am just a beginner in this topic, and i didn't do it like u did it. instead i broke it down all the way and did it. I know it is stupid but i was not so sure so..... but i did check the answer and it was correct.

3. Oct 23, 2011

### Xyius

I got my answer to be his answer. My main confusion was linking the formulas to the vector operation in the last step.