# Help on Vectors & Geometry

posted by .

(a) Given that A= 3i - j + 2k and
B=2i + 3j - k find A x B

(b) if A= i + j, B= 2i - 3j + k and
C= 4j - 3k
find (i) (AxB)x C
(ii) Ax(BxC)

• Help on Vectors & Geometry -

I will do one. These are much easier to do as matrix multipication on your calc, I would learn to do that.
1)
AxB= (3i-j+2k)x(2i+3j-k)
= 3*3ixj-3ixk-2jxi+jxk+4kxi+6kxj
well, ixj=k
jxk=i
kxi=j (and the opposite order means -)
AxB= 9k+3j+2k+i+4j-6i
check that, and combine terms.

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