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# OCR C4 (not mei) 18th June 2013 revision watch

1. (Original post by eggfriedrice)
I got t=1 and two stationary points ._.
As did I. All these conflicting answers!
2. (Original post by Dizzy in my Head)
As did I. All these conflicting answers!
Yeah, I plotted the graph and there are 2 stationary points. But why?
3. (Original post by Dizzy in my Head)
As did I. All these conflicting answers!
Let's be honest, no one knows what the ****'s happening or what they're talking about.
4. 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?
5. (Original post by eggfriedrice)
I got t=1 and two stationary points ._.
Same. So so worried now.
6. For t it was a cubic so I think it was just one stationary point...
7. (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).
8. Mr M, where art thou?

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9. Forgot to substitute u back in.... Same mistake every time
10. 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
11. 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...
12. (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?
13. (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
14. (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
15. (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.
16. How do you do the integral of tan2x question?
17. (Original post by Croydon'Stepper)
Dont worry, so did I and most of my year. Just realised marks here and there missed too
(Original post by Dizzy in my Head)
No. I agree. I thought is was dreadful. 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
18. (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
19. (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?
20. Anyone got a rough idea on grade boundaries?

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