Is there a vector proof for (u x (v+w)) . r = (u . w)(v . r) - (u . v)(w . r)?

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SUMMARY

The discussion centers on proving the vector identity (u x (v+w)) · r = (u · w)(v · r) - (u · v)(w · r). The original poster simplified the left-hand side to (r x u) · v + (r x u) · w but was uncertain about further steps. A participant identified a misprint in the original statement, suggesting the correct identity is (u x (v x w)) · r = (u · w)(v · r) - (u · v)(w · r). This correction clarifies the proof's direction and validity.

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Homework Statement


Show that (u \times (v+w))\cdot r = (u \cdot w)(v \cdot r) - (u \cdot v)(w \cdot r)

Homework Equations





The Attempt at a Solution


So far I have been able to simplify the LHS to:
(r \times u)\cdot v + (r \times u) \cdot w but don't know how to proceed from there.

In fact, I don't know if this problem is even solvable using only vector identities, i.e. without having to prove using components.

All help is appreciated!

BiP
 
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Hi Bipolarity! :smile:

It's a misprint :rolleyes:

try (u \times (v \times w))\cdot r = (u \cdot w)(v \cdot r) - (u \cdot v)(w \cdot r) :wink:
 
Thanks tiny-tim!

BiP
 

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