Not sure if this is the correct section. I apologize if it's not.(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

For any vectors [itex]\vec{a}, \vec{b}, \vec{c}[/itex] show that:

[itex](\vec{a} \times \vec{b} ) \times \vec{c}[/itex]

lies in the plane of [itex]\vec{a}[/itex] and [itex]\vec{b}[/itex]

2. Relevant equations

3. The attempt at a solution

I assigned [itex]\vec{a} = (e,f,g), \vec{b} = (x,y,z), \vec{c} = (s,t,u)[/itex]

then I used the cross product formula and got:

(u(gx-ez)-t(ey-fx), s(ey-fx)-u(fz-gy), t(fz-gy)-s(gx-ez))

which expanded comes to:

(gux-ezu-tey+tfx, sey-sfx-fuz+yug, zft-tgy-sgx+sez)

I'm not sure if that helps...

Thanks.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Cross Product Vector Proof

**Physics Forums | Science Articles, Homework Help, Discussion**