January 23, 2017

Homework Help: to bobpurlsey

Posted by steve on Tuesday, January 23, 2007 at 2:29pm.

I had the same answer as you:

except I subtracted i-i = 0

Given vectors A= (Axi + Ayj), B= (Byj+Bzk) and C= (Cyj + Czk).

a) find the triple product of these vectors defined by A dot (BxC) in terms of the vector components.

I get 0 as the answer (i-i)

(Byj+Bzk) x (Cyj + Czk).
jxj is zero
jxk is i, so there is a By*Cz i term.
kxj is -i, so there is a - Bz*Cz i term
How do you on Earth get those to add to zero?

although I appreciate the comments, it seems to me there is a subtle 'note' that would have taught me that one cannot add vectors that are not on the same plane.

for example, I was subtracting your kxj is -i with the i term (which is not on the same plane or axis). That is why I got zero. If there are two negative, then I suppose it should be -2 (unless here again, I violate rule mentioned above) Thx for your help. I would also appreciate if you simply put the final answer. It is obvious, I did not understand the explanations. Thx again.

Final answer: what is it. I see -i, then I see another i. Nothing is mentioned wheter I should add like terms to get the ZERO that I god. Thx again.

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