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Taylor expansion

  • #1

Homework Statement


Could someone please explain how the taylor expansion of 1/(r-r') turns into
( 1/r+(r'.r)/r^3 + (3(r.r')^2-r^2r'^2)/2r^5 +...)


Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
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i think it should be [itex]\frac{1}{|\vec{r}-\vec{r'}|}[/itex] yes?

use the 3d taylor expansion formula

[itex]\phi(\vec{r}+\vec{a})=\sum_{n=0}^{\infty} \frac{1}{n!} (\vec{a} \cdot \nabla)^n \phi(\vec{r})[/itex] with [itex]\phi(\vec{r}+\vec{a})=\frac{1}{|\vec{r}-\vec{r'}|}[/itex]
 

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