# Index notation

Hello world,

Index notation is driving me crazy: why on Earth is ∂_i 1/r = -x_i/r^3 ?

I would expect it to be -x_i/r^2...

Thanks for commenting

## Answers and Replies

tiny-tim
Science Advisor
Homework Helper
welcome to pf!

hello ellocomateo! welcome to the world!

(try using the X2 and X2 buttons just above the Reply box )

∂r/∂x = … ?

Oh, you mean chain rule and ∂r/∂i=xi/r
Thanks!