OCR C4 (not mei) 18th June 2013 revision

Forgot what angle I was getting in the vectors question, so I did 180-x to get 8.68. Drop 1 there.

Not really a marking point, but for the second binomial expansion when it says write in powers of 1/x, would they mean the answer given in the unofficial mark scheme or to write it as -(1/x)^2 + 3(1/x)^3 + 6(1/x)^4, or whatever it was. Either way I wrote both.

Didn't get an exact value of 28/3 for the pyramid, but I gave 9.33 to 3 sf, that should hopefully be enough. Quite a tough paper, but not unfair.

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Reply 821

TheSneakyBadger

Original post by The Coxmobil

I don't suppose anyone got a Ln of a Ln at any point?

I did

can't remember when but I did.

Reply 822

Mr M (jr)

1

Ok, I've put a mark scheme here: http://www.thestudentroom.co.uk/showthread.php?t=2384831&p=43220805#post43220805

Reply 823

alastair999100

Original post by Mr M

I've looked now. Are there any questions that people are unsure about and would like a second opinion on?

For 5 ii):

I got completely the wrong integral, but still put limits in and presented my answer in the form AlnB

How many marks would I lose? (/5)

(edited 10 years ago)

Reply 824

TheSneakyBadger

Original post by Snakefingers13

Forgot what angle I was getting in the vectors question, so I did 180-x to get 8.68. Drop 1 there.

Not really a marking point, but for the second binomial expansion when it says write in powers of 1/x, would they mean the answer given in the unofficial mark scheme or to write it as -(1/x)^2 + 3(1/x)^3 + 6(1/x)^4, or whatever it was. Either way I wrote both.

Didn't get an exact value of 28/3 for the pyramid, but I gave 9.33 to 3 sf, that should hopefully be enough. Quite a tough paper, but not unfair.

Posted from TSR Mobile

you wouldn't lose one for that 8.68, it didn't specify which angle surely?

Reply 825

The Coxmobil

Original post by DoeADeer

I think I remember getting that and being like wtf. Ahh I can't remember which question it was...

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ahhh thanks, hate that feeling in an exam where you're sure that in no way can your answer be right haha

Reply 826

Stardust95

Original post by DoeADeer

I think I remember getting that and being like wtf. Ahh I can't remember which question it was...

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I did for the substitution one when I put x back in.. Ln ( 1 + lnx ) + ... Something like that :smile:

Reply 827

Mr M (jr)

1

Original post by QuestionsQ

Mr M - would greatly appreciate your help. At the very beginning of Q8 part I - I subbed in the value of t instead of r into 1.08=k/sqrtR - everything else in my working was correct - how many do you think I would lose for doing something so silly? Also, my y co ordinates for Q4 were wrong for the final 2 x-co ordinates. All my x values were correct. Greatly appreciate what you do here -

Q8: lose 2 or 3 probably.

Q4: probably only lose 1. Max 2.

Reply 828

Mr M (jr)

1

Original post by TheSneakyBadger

you wouldn't lose one for that 8.68, it didn't specify which angle surely?

It did; it asked for angle BAC. Only 171 (or possibly 360-171) would be acceptable.

Reply 829

TheSneakyBadger

Original post by Mr M (jr)

It did; it asked for angle BAC. Only 171 (or possibly 360-171) would be acceptable.

How would it specify if it had wanted 8.68?

Reply 830

username1044462

10

Reckon 64/72 is going to be 90%?

Reply 831

SJ12345

Original post by Mr M

I've looked now. Are there any questions that people are unsure about and would like a second opinion on?

To integrate tan2x ive done 1/2lnsecx instead of 1/2lnsec2x. How many marks will i lose out of 5?

Original post by SJ12345

To integrate tan2x ive done 1/2lnsecx instead of 1/2lnsec2x. How many marks will i lose out of 5?

drop 1

Reply 833

sj_1995

To integrate tan 2x, I used a simple substitution of u =2x, to tanu/2 then changed my limits etc. and got to the correct answer. That would be fine wouldn't it? They didn't specify a particular method of doing it did they?

Reply 834

Maid Marian

20

Original post by Mr M

drop 1

Mr M, could you please tell me if you think I'd get ANY marks at all on number 8, because I put

dr = -k rootx.
dt

Which I know is horrifically wrong, I just forgot what inversely proportional meant. Would I get any marks at all for the whole question? :frown:

Reply 835

SJ12345

Original post by Mr M

I've looked now. Are there any questions that people are unsure about and would like a second opinion on?

Is the angle 8.7 or 171.3?
Thank you Mr M! :biggrin:

Reply 836

username973061

Original post by Mr M

I've looked now. Are there any questions that people are unsure about and would like a second opinion on?

Hi, I wonder if you could guess at how many marks overall I would have lost from these mistakes:

1) Putting 1/72 rather than 1/81 because I'm such an idiot
5ii) Integrating tan2x correctly but then putting the limits in as if it were 0.5lnsecx rather than sec2x..........
7iii) Doing all the right method but multiplying by 1/2 instead of 1/3 because I apparently can't read.
8) leaving the equation of r as 2/3(r)^3/2 rather than rearranging to get r on its own

I also said that the stationary point (0,3) was a maximum not a minimum, is this right? and if not, how many marks

Thanks!

Reply 837

GeorgeHead