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# AQA A2 Mathematics MPC4 Core 4 - 9th June 2015 [Discussion & unofficial markscheme] watch

1. (Original post by 2014_GCSE)
What I've never understood about the June 2013 Vector question (6d) is that why is it that just because the area of a triangle is 3 times as big, that the BASE is 3 times as big (that's how you find out the co-ordinates)? Couldn't it have a bigger area in other ways. http://filestore.aqa.org.uk/subjects...4-QP-JUN13.PDF

Can anyone shed some light on this?
no cos perpendicular height of triangle must be the same.
and the length must lie along AB and so must be 3AB to make area 3 times as big
2. (Original post by maattwileman)
your PS is ACTUALLY OS, RS is then OS - OR
Yeah I got the OS thing. What I mean is when I did the dot product I used SR instead of RS.

Why should it be RS? Shouldn't they both be facing out?
3. (Original post by redherring18)
I'm confident with all the concepts of the vectors in terms of distance between 2 vectors, parallel, intersecting, skew lines...blah blah.

However, I always seem to be confused by what is often the final question of the section which most of the time asks you to apply your knowledge to a shape...

Has anyone got any tips when tackling these styles of questions? :/
Hi a tip which I would give is, I always read the question really slowly and highlight the key information, generally in all the vectors questions you have to apply your answers from the previous part to it, I think of it like solving a puzzle
4. (Original post by Alexandrite)
Yeah I got the OS thing. What I mean is when I did the dot product I used SR instead of RS.

Why should it be RS? Shouldn't they both be facing out?
A rule I have used is on these type of questions the point you have to use for finding the coordinate of a value (in this case S) first when subtracting. Example in this case is RS, so use the s value and then take away the r value, use whatever you have formed an equation for finding a coordinate first
5. (Original post by Alexandrite)
Yeah I got the OS thing. What I mean is when I did the dot product I used SR instead of RS.

Why should it be RS? Shouldn't they both be facing out?
Both are perpendicular, yes. Using SR in the dot product will produce the same result (your chosen multiplier = -1, for this question).
A rule I have used is on these type of questions the point you have to use for finding the coordinate of a value (in this case S) first when subtracting. Example in this case is RS, so use the s value and then take away the r value, use whatever you have formed an equation for finding a coordinate first
Yeah I'll pick that up when doing the next exams

(Original post by datpr0)
Both are perpendicular, yes. Using SR in the dot product will produce the same result (your chosen multiplier = -1, for this question).
With SR I got 1
7. Could someone please explain Jan 2013 question 7 bi to me?
8. Is anyone else feeling, after C3, just what will be will be, with this paper tomorrow? I usually get so nervous but now I feel so robbed of an A* grade I almost just accept an overall A now. I am not gonna put myself under insane pressure anymore, just taking it easy doing mocks today.
9. You know when you have 'cosOBA' and you need to find the angle?

Which vectors do you use?

Is it OB.BA/|OB|.|BA|?

10. (Original post by Hexaneandheels)
Is anyone else feeling, after C3, just what will be will be, with this paper tomorrow? I usually get so nervous but now I feel so robbed of an A* grade I almost just accept an overall A now. I am not gonna put myself under insane pressure anymore, just taking it easy doing mocks today.
How is you not being prepared for the paper being robbed?
11. Any help on whole of part b! binomial question

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12. (Original post by Jankie)
You know when you have 'cosOBA' and you need to find the angle?

Which vectors do you use?

Is it OB.BA/|OB|.|BA|?

OB and BA.
13. (Original post by Alexandrite)
Yeah I'll pick that up when doing the next exams

With SR I got 1
I got -6 - 6[multiplier] = 0 => [multiplier] = -1.
14. I know this is super last minute but I've had to have a lot of time away from school due to personal reasons and haven't been able to learn vectors fully, does anyone know of a good resource online that I could learn it from? Or have any tips?
15. (Original post by ubisoft)
OB and BA.
Hi, thank you! Does that mean, if you have for example ABC, you then use AB and BC?
16. (Original post by 14Billie)
I know this is super last minute but I've had to have a lot of time away from school due to personal reasons and haven't been able to learn vectors fully, does anyone know of a good resource online that I could learn it from? Or have any tips?
This helped me

http://www.mathsbox.org.uk/revisionn...on%20Notes.pdf
17. (Original post by 14Billie)
I know this is super last minute but I've had to have a lot of time away from school due to personal reasons and haven't been able to learn vectors fully, does anyone know of a good resource online that I could learn it from? Or have any tips?
http://www.mrbartonmaths.com/resourc...evision/C4.pdf

good luck
18. 8a) is ln(y) = -cos(t) + c but in the mark scheme they changed the -cos(t) to A and this gave the final mark. Why did they do this? And would we have to do it in all questions of this type?

Thanks!
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19. (Original post by Jankie)
Hi, thank you! Does that mean, if you have for example ABC, you then use AB and BC?
Yes. The angle is always between the 2 vectors. B is the angle in the middle, made by AB and BC
20. (Original post by ubisoft)
Yes. The angle is always between the 2 vectors. B is the angle in the middle, made by AB and BC

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