Posted by **Wellness** on Thursday, October 29, 2009 at 3:11pm.

(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 -
**bobpursley**, Thursday, October 29, 2009 at 6:19pm
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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