vector analysis, grad,div

Can anyone help me with this problem expecially c) . I believe you use a) to solve it but I don't know how.

For r = (x,y,z)

a) show that http://latex.codecogs.com/png.latex?...C%5E%7Bn-2%7Dr
b) show that http://latex.codecogs.com/png.latex?...r.a%29%20=%20a if http://latex.codecogs.com/png.latex?%20a is a constant vector
c) find http://latex.codecogs.com/png.latex?%5Cphi such that http://latex.codecogs.com/png.latex?...%7C%5E%7B4%7Dr

Choose

phi ( r ) = ( 1 / 6 ) | r |^6

sorry how did you come to this?

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Originally Posted by riptorn70

sorry how did you come to this?

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n - 2 = 4 so, n = 6 .

Thank you, Fernando Revilla.

Quote:

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Originally Posted by riptorn70

Thank you, Fernando Revilla.

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You are welcome!