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OCR C4 (not mei) 18th June 2013 revision

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Original post by Dizzy in my Head
As did I. All these conflicting answers! :confused:


Let's be honest, no one knows what the ****'s happening or what they're talking about.
Can someone please answer this question.... when you had to integrate x^8 ln3x... i put ln3x as u and when you differentiate it, it simplifies to 1/x, but when 1/x is integrated you get lnx not ln3x why is that?
Original post by eggfriedrice
I got t=1 and two stationary points ._.


Same. So so worried now. :frown:
Reply 423
Avatar for h2shin
h2shin
9
For t it was a cubic so I think it was just one stationary point...
Original post by ihatepeople37
Can someone please answer this question.... when you had to integrate x^8 ln3x... i put ln3x as u and when you differentiate it, it simplifies to 1/x, but when 1/x is integrated you get lnx not ln3x why is that?


It's because when you integrate, there's a constant. That constant will be ln(3).
Reply 425
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DoeADeer
9
Mr M, where art thou?

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Reply 426
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h2shin
9
Forgot to substitute u back in.... Same mistake every time
There are 3 stationary points because you cancelled cosx's and to do that you have to find the solution to cosx=0 i.e. x=pi/2
3) Skew
4) (pi/2 ,1), (pi/6 , 3/2)
5ii) 1/2 ln (root 13)
cant remember the question: (0,3)

Some of the answers i remember...
Original post by Emmalacrosse
There are 3 stationary points because you cancelled cosx's and to do that you have to find the solution to cosx=0 i.e. x=pi/2


Yeah see this is what I thought, but I plotted the graph on an online plotter and there's only two. Why is this?
Original post by Vip3rgt9
It's because when you integrate, there's a constant. That constant will be ln(3).

ok... still not 100% sure but there's nothing I can do now...could have done with 15 more mins
Reply 431
Avatar for SJ12345
SJ12345
Original post by ihatepeople37
Can someone please answer this question.... when you had to integrate x^8 ln3x... i put ln3x as u and when you differentiate it, it simplifies to 1/x, but when 1/x is integrated you get lnx not ln3x why is that?


ln(3x)= ln3 + ln x. ln 3 is a constant and so differentiates to zero while lnx gives 1/x
Original post by ihatepeople37
ok... still not 100% sure but there's nothing I can do now...could have done with 15 more mins


It's ok though. You are right in thinking that it differentiated to 1/x.
Reply 433
Avatar for SJ12345
SJ12345
How do you do the integral of tan2x question?
Original post by Croydon'Stepper
Dont worry, so did I and most of my year. Just realised marks here and there missed too :frown:


Original post by Dizzy in my Head
No. I agree. I thought is was dreadful. :mad: I'm so angry with myself! I can't wait for someone to post an unofficial mark scheme.


Phew.
I'm so angry with myself too. I let myself down so much, I messed up just about every question in some way ... I'm just in a shocked state of horror atm :frown:
Original post by SJ12345
ln(3x)= ln3 + ln x. ln 3 is a constant and so differentiates to zero while lnx gives 1/x

oh okay.... i am such a nob
Original post by SJ12345
How do you do the integral of tan2x question?


Oh yeah, I messed up that question. Had a total mindblank.

Somebody enlighten us?
Anyone got a rough idea on grade boundaries?
Original post by g33kym0nk3y
3) Skew
4) (pi/2 ,1), (pi/6 , 3/2)
5ii) 1/2 ln (root 13)
cant remember the question: (0,3)

Some of the answers i remember...


I got 0,3 for something as well!

But for number 4 my y values were the same as each other (though I can't remember what it was)... another question down the drain.
Original post by Maid Marian
I got 0,3 for something as well!

But for number 4 my y values were the same as each other (though I can't remember what it was)... another question down the drain.


Relax, I probably got it wrong... My life sucks anyways.

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