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# C4 Vectors Question watch

1. What does it mean by "between diagonals of the parallelogram"?
I did scalar product of AB and AC though I got the wrong answer. I tried other vectors though I kept getting an error whenever I subbed the values in my calculator.
2. You just need to find the angle between AB and AC, I think. It's the dot product divided by the product of the magnitudes of the vectors, if that makes sense
3. If you draw a line from one corner to the opposite corner of the parallelogram,that's a diagonal. Repeat for the other 2 corners and that's he othe diagonal. They meet at a point and you're finding the acute angle between them, not the obtuse angle.
4. What answer did you get?
5. (Original post by L-Tyrosine)
You just need to find the angle between AB and AC, I think. It's the dot product divided by the product of the magnitudes of the vectors, if that makes sense
Done that but not got the same answer as one in mark scheme

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6. (Original post by B_9710)
What answer did you get?
I got 35
The m.s. says 58.5

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7. (Original post by TSRforum)

What does it mean by "between diagonals of the parallelogram"?
I did scalar product of AB and AC though I got the wrong answer. I tried other vectors though I kept getting an error whenever I subbed the values in my calculator.
8. (Original post by TeeEm)

Edit: should be root 29 instead of 53

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9. I am sorry but I cannot make up from that what are you doing.
I expect to see the vectors for the diagonals first (or equivalent direction vectors)
10. (Original post by TeeEm)
I am sorry but I cannot make up from that what are you doing.
I expect to see the vectors for the diagonals first (or equivalent direction vectors)

I just divided AC by 2 to get I + 2J +3/2K. I really don't know what acute angle I'm looking for ...

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11. (Original post by TSRforum)

I just divided AC by 2 to get I + 2J +3/2K. I really don't know what acute angle I'm looking for ...

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you need the vector BC or CB (the other diagonal)
12. (Original post by TeeEm)
you need the vector BC or CB (the other diagonal)
That's just -AC + AB, right? So it's -3i + -4j +0k. What do I do with that?

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13. (Original post by TSRforum)
That's just -AC + AB, right? So it's -3i + -4j +0k. What do I do with that?

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correct
dot it with AD
14. (Original post by TeeEm)
correct
dot it with AD
Got math error in calculator

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15. (Original post by TSRforum)
Got math error in calculator

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I cannot see what your are inputting
Do you know how to dot vectors?
16. (Original post by TeeEm)
I cannot see what your are inputting
Do you know how to dot vectors?
Yes.

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17. check the dot product
18. (Original post by TeeEm)
check the dot product
Oh I added instead of multiplying 😐

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