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# Vectors.. again. watch

1. I suspect I went wrong somewhere/am stuck on part (b)

Sigh, I need some sleep.
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2. (Original post by edothero)
I suspect I went wrong somewhere/am stuck on part (b)

Sigh, I need some sleep.
my approach would be different

Midpoint of AB is (2, -1/2, 1/2)

M must also be the midpoint of OC

Since O(0,0,0), C(4,-1,1)

any good?

I can also do one with "vector vectors"
3. (Original post by edothero)
I suspect I went wrong somewhere/am stuck on part (b)

Sigh, I need some sleep.

Do you know dot product, cross product or both?
4. (Original post by TeeEm)

Do you know dot product, cross product or both?
just the dot product

5. (Original post by edothero)
just the dot product

are you on a calculator course or non calculator?
6. (Original post by TeeEm)

are you on a calculator course or non calculator?
It's Edexcel C4; calculator.
7. (Original post by edothero)
It's Edexcel C4; calculator.
then I doubt if they want exact answer

Use the OA and AB to find angle OAB (dot product)

then trigonometric area of the triangle x2
8. I got around 20.7
9. (Original post by TeeEm)
then I doubt if they want exact answer

Use the OA and AB to find angle OAB (dot product)

then trigonometric area of the triangle x2
Thanks again!
10. (Original post by edothero)
Thanks again!
no problem
11. (Original post by edothero)
I suspect I went wrong somewhere/am stuck on part (b)

Sigh, I need some sleep.
I managed to get through A2 maths without being able to do the most basic vectors questions so i'm no use, good luck!

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