How to Prove ∇^2 (1/r) = 0 in Cartesian Coordinates?

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SUMMARY

The discussion focuses on proving that the Laplacian operator, ∇², applied to the function 1/r in Cartesian coordinates equals zero for r > 0. Participants shared their attempts at differentiating the components of 1/r with respect to x, y, and z, but initially encountered errors in their calculations. Ultimately, the original poster resolved the issue, attributing it to minor miscalculations. The conversation highlights the importance of careful differentiation and verification in vector calculus.

PREREQUISITES
  • Understanding of vector calculus, specifically the Laplacian operator ∇².
  • Familiarity with Cartesian coordinates and their application in physics.
  • Knowledge of differentiation techniques in multivariable calculus.
  • Basic understanding of the function 1/r and its properties in three-dimensional space.
NEXT STEPS
  • Review the derivation of the Laplacian operator in Cartesian coordinates.
  • Study the application of the Laplacian in different coordinate systems, such as spherical coordinates.
  • Practice solving similar problems involving vector calculus and Laplacians.
  • Explore common pitfalls in differentiation of multivariable functions to improve accuracy.
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Students and professionals in mathematics, physics, and engineering who are working with vector calculus and need to understand the application of the Laplacian operator in various coordinate systems.

johnaphun
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Homework Statement



Write down an expression for ∇^2 in Cartesian co-ordinates and, by expressing the displacement vector r in Cartesians show that:

∇^2 ⎛ 1/r ⎞ = 0 for r > 0.

Homework Equations



I can do the first part of the question and i know how to show that ∇^2 ⎛ 1/r ⎞ = 0 in spherical polars but i think I'm missing something here.

The Attempt at a Solution



I tried differentiating the x component of 1/r twice w.r to x and likewise with the y and z components but I'm not getting zero.
 
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hi johnaphun! welcome to pf! :smile:

(try using the X2 icon just above the Reply box :wink:)
johnaphun said:
I tried differentiating the x component of 1/r twice w.r to x and likewise with the y and z components but I'm not getting zero.

it should add up to zero :confused:

show us your full calculations, and then we'll see what went wrong :smile:
 
Thanks for the quick response and apologies for my slow one!

Don't worry i manage to solve it in the end, silly miscalculations on my part.

Thank you for the help anyway!
 

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