Cross Product Proof: u X v X w = u X (v X w)

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SUMMARY

The discussion centers on proving the vector identity (u X v) X w = u X (v X w) if and only if (u X w) X v = 0. Participants emphasize the necessity of demonstrating both implications: P → Q and Q → P. The relationship (u X v) = -(v X u) is also highlighted as a fundamental property of cross products, aiding in the proof process. The use of the Einstein summation convention is suggested for simplifying calculations.

PREREQUISITES
  • Understanding of vector cross product properties
  • Familiarity with the Einstein summation convention
  • Knowledge of scalar multiples in vector spaces
  • Basic proficiency in vector calculus
NEXT STEPS
  • Study the properties of vector cross products in-depth
  • Learn how to apply the Einstein summation convention in vector proofs
  • Explore scalar multiples and their implications in vector equations
  • Practice proving vector identities using both direct and contrapositive methods
USEFUL FOR

Students and educators in mathematics or physics, particularly those focusing on vector calculus and linear algebra, will benefit from this discussion.

MJC684
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Homework Statement



(u X v) X w = u X (v X w) Iff (u X w) X v = 0

Homework Equations



(u X v) = -(v X u)

The Attempt at a Solution



I know that I am supposed to prove this by proving P --> Q and Q --> P
I know that if (u X w) X V = 0 then (u X w) is a scalar multiple of v.

How do i deduce Q from P and P from Q?
 
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Hi MJC684! :smile:

What is (u X v) X w - u X (v X w) ? :wink:

(use the Einstein summation convention if you know it, otherwise use coordinates)
 

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