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

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/AQA-MPC4-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

Reply 1081

Alexandrite

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?

Reply 1082

bilalahmad02

1

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

Reply 1083

bilalahmad02

1

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

Reply 1084

datpr0

2

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).

Reply 1085

Alexandrite

2

Original post by bilalahmad02

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

Reply 1086

Tiwa

7

Could someone please explain Jan 2013 question 7 bi to me?

Reply 1087

Hexaneandheels

4

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.

Reply 1088

Jankie

3

You know when you have 'cosOBA' and you need to find the angle?

Which vectors do you use?

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

SOMEONE PLEASE HELP IM STRESSING SO MUCH :frown:

Reply 1089

ubisoft

3

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?

Reply 1090

Jimmy20002012

4

Any help on whole of part b! ImageUploadedByStudent Room1433771048.183159.jpg

binomial question

Posted from TSR Mobile

Reply 1091

ubisoft

3

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|?

SOMEONE PLEASE HELP IM STRESSING SO MUCH :frown:

OB and BA.

Reply 1092

datpr0

2

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.

Reply 1093

14Billie

1

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?

Reply 1094

Jankie

3

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?

Reply 1095

Jankie

3

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 :smile:

http://www.mathsbox.org.uk/revisionnotes/AQA%20Core%204%20Revision%20Notes.pdf

Reply 1096

amyrah

2

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/resources/a%20level%20revision/C4.pdf

good luck :smile:

Reply 1097

amyrah

2

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!

Screen Shot 2015-06-08 at 14.59.43.png25.1KB

Reply 1098

ubisoft

3