OCR (not MEI) Core 3 - 19/01/2011

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Reply 260

jackdelderfield

i found that gf(x)= (lnx)^2 + 8 so gf'(x)= 1/x^2 therefore it equals 1/e^3

I differentiated (lnx)^2 differently cause it was in brackets, so mine came out at 2x1/x(lnx).

Reply 261

a.nk

Original post by jayjay1

how did everone expand tanacotatan2a?

It was TanXCot2XTan4X and if you take each individual part and work it out by subbing in TanX=1/4 then you get the answer. It was long though.

Reply 262

EdwardSAS

Original post by DaveGBG

Anyone else have a time issue with this paper?

I did, got to the end with about a minute to spare...then realised there was a question 9.

Not that it mattered - I couldn't do it anyway, I just quickly differentiated f(x) in the hope of getting a method mark.

Reply 263

CitizensUnited

Original post by jayjay1

how did everone expand tanacotatan2a?

I used cot x = 1 / tan x , then did the tan 2x expansion, cancelled and substituted tan x for 1/4 , then simplified evverything. I think I got 225/384 or something.

Reply 264

Vivvy15x

Worst exam I have ever sat in my life!
only confident with the 1 mark question, 'tan2a'

Reply 265

jayjay1

Original post by CitizensUnited

I used cot x = 1 / tan x , then did the tan 2x expansion, cancelled and substituted tan x for 1/4 , then simplified evverything. I think I got 225/384 or something.

hey i did the same as you but i got 32/135
anyway hope i get marks for method

Reply 266

godexists1234

Original post by jackdelderfield

I differentiated (lnx)^2 differently cause it was in brackets, so mine came out at 2x1/x(lnx).

i wasnt sure how to differentiate it, so i used the product rule with both u and v = to lnx, making (lnx)^2 and got something like 2(lnx)/x

Reply 267

Dunney101

Original post by DaveGBG

Anyone else have a time issue with this paper?

Yes majorly! i had like 5 mins to do question 9.ii) 9.iii) i was panicing so much that i just differentiate the fucntion and basically left the last 9.iii) . I couldnt even comprehend what to do once i differentiated lol i think just on question 9 i lost 10 marks. cool

(edited 13 years ago)

Reply 268

jayjay1

whers mr M with the answers

Reply 269

Jin3011

For the tan(theta) question => cot(theta)=4 tan(theta)=1/4

tan*(1-tan^2(theta)/2tan(theta))*(2tan(2theta)/1-tan(2theta))

I did inverse tan on tan(theta)=1/4 to get theta to get 0.244... since we've got 2theta as well I did (theta)*2=0.4899 then I did tan(2theta)=>tan(0.4899) =8/15

So you have tan(theta)=1/4 and tan(2theta)=8/15
and put it back into the equation to get
225/322 I think. Am I right?

Reply 270

jackdelderfield

Original post by godexists1234

i wasnt sure how to differentiate it, so i used the product rule with both u and v = to lnx, making (lnx)^2 and got something like 2(lnx)/x

Interesting. Substituting e^3 seems to give the same answer from both, 6/e^3?

Reply 271

thurin

Let's just say that C3 and I will be meeting again in June. :\

Reply 272

ElMoro

Original post by Jin3011

I didn't check your method but your answer was the same as mine :wink:

Reply 273

Flint_09

every1 how did you find this paper overall on a scale of 1-10 with 1 being the easiest and 10 the hardest!

Reply 274

Jin3011

Original post by ElMoro

I didn't check your method but your answer was the same as mine :wink:

Reply 275

Munchy5793

Original post by I0144

Not sure whether these are right, relooked at the hard questions at home and i've got these.

1) x = a/3 and -3a
2) Two stationary points are (-3,0) and (-5,24)
3) 45000
4i) 25Sin(theta+16.3)
ii) theta= 12.4 and 135
5) 12(pi)ln25
6ii) 2.398
7i) x = (e^8-8)^0.5
ii) e^x
iii) 6/e^3
iv) 20.3
8aii) 3pi-alpha
bii) 225/322
9ia) f'(x) = 2(e^2x+3/e^2x); therefore e^2x > 0; so f'(x) > 0
b) x > ln3/4
ii) Range of g(x) >= k^0.5 (1-k)

So much easier when you do it at home...

For The Last One Im Pretty Sure Its 2rootk
Apart From That Im Sure They Are Right

Reply 276

Jin3011

Original post by Flint_09

every1 how did you find this paper overall on a scale of 1-10 with 1 being the easiest and 10 the hardest!

Not sure tbh, doing it at home now seems much easier than in the exam hall.
But on first sight, and comparing to previous papers, I'd say 7+ln(e^1/2)/10 :wink:

(edited 13 years ago)

Reply 277

Munchy5793

Original post by Flint_09

every1 how did you find this paper overall on a scale of 1-10 with 1 being the easiest and 10 the hardest!

8/9

Reply 278

Dunney101

Original post by Flint_09

every1 how did you find this paper overall on a scale of 1-10 with 1 being the easiest and 10 the hardest!

Without including question 9, i would give it 7-8 out of 10. Including question 9 i would say 10.

Reply 279

Haz13

Question 9 was really really quite hard. Especially the last question worth 5.

I'm hoping I have got around 62 on the paper... might get lucky and get an A* but I have a feeling that's an A.