Mr M's OCR (not OCR MEI) Core 2 Answers May 2013

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For 7.ii i got the equation of the tangent right but i integrated it wron but my method was still correct after that.
For 8.iii i got to the point of x=2/(log2(a)-log2(b))
How many marks would i get on each?

Reply 301

Substitution

Original post by Mr M

That's the correct method. The C2 specification states that knowledge of C1 may be required. This continues at A2 - C4 assumes knowledge of C1, C2 and C3.

wish I knew that, I did the same but forgot how to differentiate so did dy/dx= then decreased power and divided by the power do you think I will get any marks? I continuined to calculate the area under the graph by doing graph minus triangle??

also for logs I did:
a^x=4b^x
xlog2 a=log2 4+xlog2 4b
x log2 a = 2 + xlog2 4b times all by a -.-
x log 2 aa - x log2 4ab= 2
then I can't remember it went downhill but I did somehow end up with th log. how many marks can I expect?

Reply 302

Mr M

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Original post by DutchyBoy

7ii) get 3 or 4 marks

8ii) get 2 marks

Reply 303

Mr M

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Original post by BenChard

I expect you will get 2 marks for 7ii), one for attempting to differentiate and one for subtracting the triangular area.

Looks like 2 marks for the logs.

Reply 304

Substitution

Original post by Mr M

I expect you will get 2 marks for 7ii), one for attempting to differentiate and one for subtracting the triangular area.

Looks like 2 marks for the logs.

thanks. I think I've lost 9+/-1, would that be an a or is it borderline? thanks

Reply 305

Namige

Original post by BenChard

thanks. I think I've lost 9+/-1, would that be an a or is it borderline? thanks

I think the grade boundaries will be quite high, but you should be okay with 61/62. But it would be a low A.

Posted from TSR Mobile

Reply 306

Substitution

Original post by Namige

I think the grade boundaries will be quite high, but you should be okay with 61/62. But it would be a low A.

Posted from TSR Mobile

thanks, can only hope now!

Reply 307

science-oliver

Mr M, on 7ii) I differentiated the tangent then found the equation of the line then made it =0 and then got confused with the integration as I integrates between 5/3 and 1, how many marks would I have dropped out of the 5?

Reply 308

Mr M

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Original post by BenChard

thanks. I think I've lost 9+/-1, would that be an a or is it borderline? thanks

I don't guess grade boundaries.

Reply 309

Mr M

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Original post by science-oliver

Well that is potentially all correct. Are you saying you made a mistake with your integration? If so, lose 1 or 2 marks.

Reply 310

ZCYZSRIW

How do you solve the last question?? I couldn't even begin it to find even one value of x. I wrote down 3 correct answers for x through complete guesses at the end but no working, will i get any marks?

Reply 311

science-oliver

Original post by Mr M

Well that is potentially all correct. Are you saying you made a mistake with your integration? If so, lose 1 or 2 marks.

I thought the part where I integrated between 5/3 and 1 was wrong as I integrated between 5/3 which was right, but integrated with the wrong limit? As I didn't think you were to integrate with x=1?

Reply 312

Mr M

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Original post by science-oliver

I thought the part where I integrated between 5/3 and 1 was wrong as I integrated between 5/3 which was right, but integrated with the wrong limit? As I didn't think you were to integrate with x=1?

Oh I see. Yes the 1 limit is incorrect. Lose 2 marks I expect.

Reply 313

Mr M

Study Forum Helper

Original post by ZCYZSRIW

You were supposed to make the connection between part (iii) and part (ii) (you needed to make the substitution

x=\cos \theta

).

Correct answers in an exact form with no extra answers will gain full marks. The examiner will just assume you solved it in your head (this is perfectly possible if you know what you are doing).

Reply 314

science-oliver

Original post by Mr M

Oh I see. Yes the 1 limit is incorrect. Lose 2 marks I expect.

thank you!

Reply 315

smithstefan1995

For the last question with the logs, I had all of the logs with x on 1 side and factorised X out leaving the logs in the brackets without showing the log law loga^b = blog(a) is that okay???

This was posted from The Student Room's iPhone/iPad App

Reply 316

Mr M

Study Forum Helper

Original post by smithstefan1995

For the last question with the logs, I had all of the logs with x on 1 side and factorised X out leaving the logs in the brackets without showing the log law loga^b = blog(a) is that okay???

I have no idea what you are describing. Could you type that step out?

Reply 317

sugartown

Hi Mr M
on the first question I made the most ridiculous mistake and put 3 instead of 2 as H
I worked out all the Y values and wrote out the formula correctly (obviously with 3 instead of 2 though)
how many marks do you think I will lose?