Prove (u+v) x (u-v) = 2v x u (Cross product)

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SUMMARY

The discussion focuses on proving the vector identity (u+v) x (u-v) = 2v x u, where u and v are vectors defined as u=(x1,y1,z1) and v=(x2,y2,z2). The solution involves expanding the cross product and applying properties of cross products, specifically that u x v = -v x u and that the cross product of identical vectors is zero. The participant provides an expression for 2v x u and seeks assistance in completing the proof.

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  • Understanding of vector operations, specifically cross products.
  • Familiarity with vector notation and components.
  • Knowledge of properties of cross products, including anti-commutativity and the zero product property.
  • Basic algebraic manipulation skills for expanding expressions.
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Homework Statement



Show that (u+v) x (u-v) = 2v x u

Homework Equations



being u=(x1,y1,z1)
and v= u=(x2,y2,z2)

The Attempt at a Solution



I've got 2v x u equals:

(2y2.z1 - 2z2.y1) + (2x2.z1 - 2z2.x1) +
(2x2.y1 - 2y2.x1)

But I'm nearly to melt my mind to prove (u+v) x (u-v) = above
 
Last edited:
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Expand the product, and use that property of the cross product that uxv=-vxu and the product of identical vectors is zero.

ehild
 

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