It's question 6 of the above, just the bit at the start of step c) where you prove .
Basically, you have , and you can assume the identities proved in a) and b). Prime on a vector operator means treat r' as variable and r as constant.
What I did was;
Then using integration by parts or the product rule;
However, this is the wrong answer, as the first term won't always be zero and the second term is the required integral. The class notes I copied off the board (without understanding at the same time) seem to do the same thing I have, but the answer is definitely the one asked for, as that's what it says in the textbook.
Can anyone tell me what I'm missing. I don't know where to start looking. Thanks
EDIT: I've solved the problem - there is a typo in the question. It should say rho vanishes outside and on the boundary, which causes the extra term to disappear, by the divergence theorem. I am now really happy. Feel free to delete the thread.
Vector / Integral question - probably simple, but can't see answer. Watch
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Last edited by Octohedral; 17-05-2013 at 17:47.
- 16-05-2013 20:42