A level maths query (new spec)

For Edexcel, do we need to know how to find the direction of a 3d vector because I haven't come across direction in 3d yet but I've seen it in my homework. However, the spec seems very vague on the topic of vectors so could someone please clarify?

Thanks

Reply 1

begbie68

16

Original post by Physikoi

For Edexcel, do we need to know how to find the direction of a 3d vector because I haven't come across direction in 3d yet but I've seen it in my homework. However, the spec seems very vague on the topic of vectors so could someone please clarify?

Thanks

Yes.
It's clearly set out in the Edexcel Pure Year 2 book.
Page 339-343, with a nice bold sentence or 2 at bottom of page 340.

Reply 2

begbie68

16

Original post by Physikoi

For Edexcel, do we need to know how to find the direction of a 3d vector because I haven't come across direction in 3d yet but I've seen it in my homework. However, the spec seems very vague on the topic of vectors so could someone please clarify?

Thanks

Also look here:
https://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2017/specification-and-sample-assesment/a-level-l3-mathematics-specification.pdf

specifically 10.2 on page 27

IMO it is not vague

Reply 3

username4167452

OP

18

Original post by begbie68

Also look here:
https://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2017/specification-and-sample-assesment/a-level-l3-mathematics-specification.pdf

specifically 10.2 on page 27

IMO it is not vague

Thank you so much

Reply 4

username4167452

OP

18

Original post by begbie68

Also look here:
https://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2017/specification-and-sample-assesment/a-level-l3-mathematics-specification.pdf

specifically 10.2 on page 27

IMO it is not vague

But that works for angles with axis, does it work for direction? I tried attempting question 10 on this worksheet
https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwini9-Bt4zfAhVQThoKHaIfCP8QFjABegQIBBAC&url=https%3A%2F%2Fwww.ocr.org.uk%2FImages%2F413787-section-check-in-1.10-vectors.docx&usg=AOvVaw1tjSCStecB38LgIzXELBVf
and correctly got the resultant force as (1,-2,3) so using the textbook method I found the angle it makes with x-axis and did cos theta = 1 / root 14, howeverthis answer is incorrect

Reply 5

begbie68

16

the direction can be described as (i -2j + 3k) [or any multiple of this]
You're not asked to find an angle that this vector makes with any other direction, which means really (IMO) that this is not a good question because it is not made clear, other than in the MS, that they want the angle the vector makes with the x-y plane.

I make this angle 53.3

The answer they give is (90 - the angle between the vector and the (negative)y-axis)

In the text books I've seen, it appears that the whole of the vectors sections (in Pure1, also) have been quite rushed.

However, the questions that you'll see in specimen papers (from the exam boards) and the questions that you'll get in the actual exam, will be very clear.

A level maths query (new spec)

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