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# vectors watch

1. i think i may be over complicating this but how do i verify that
5i+3k is parallel to -3i+5k ?

thanks
2. it's not

Two vectors are parallel when one of them is ai+bj+ck and the other λ(ai+bj+ck)

where λ is a real number
3. Wow I've never understood that!! Thanks.
4. Isn't it using the dot product?

a: ni+nj+nk
b: mi+mj+mk

Cos θ = (a.b)/|a||b|
Where a.b = (ni x mi) + (nj x mj) + (nk x mk)

Since a.b = (5x3)+(-3x5) = 0

So Cosθ=0
θ= arccos 0
θ= 90° ????
5. yeh thats correct theyre perpendicular to each other u can tell by looking at the cross product whcih is =0

or vectors [a b] and [-b a] are perp..

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