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# c4 vectors

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1. In part a) (not show in the above image), they ask you to find the lengths of AB and BC. I done that correctly.. For part b, when constructing the above diagram, how do you know which way the arrows point?

Thanks
2. (Original post by xXxiKillxXx)

In part a) (not show in the above image), they ask you to find the lengths of AB and BC. I done that correctly.. For part b, when constructing the above diagram, how do you know which way the arrows point?

Thanks
The arrows should be pointing away from B, hence the arrows are in the direction BA and BC.
3. (Original post by raheem94)
The arrows should be pointing away from B, hence the arrows are in the direction BA and BC.
Why should they be pointing away from B? THanks
4. (Original post by xXxiKillxXx)
Why should they be pointing away from B? THanks
See page#69 of the edexcel C4 book.
5. (Original post by raheem94)
See page#69 of the edexcel C4 book.
Oh so vectors always point away from the angle?
6. (Original post by xXxiKillxXx)
Oh so vectors always point away from the angle?
If you want to find angle ABC.

Then the two vectors you need to consider should be in the direction pointing away from B.

AB is pointing towards B, so we use BA rather than AB.
CB is pointing towards B, so we use BC rather than CB.
7. Work out BA and BC and use the costheta formula.
8. (Original post by raheem94)
If you want to find angle ABC.

Then the two vectors you need to consider should be in the direction pointing away from B.

AB is pointing towards B, so we use BA rather than AB.
CB is pointing towards B, so we use BC rather than CB.

(Original post by DoctorVertigo)
Work out BA and BC and use the costheta formula.
Ahhh thanks

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