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# AQA Core 4 - Monday 10th June 2013 (AM) - Official Thread watch

1. The only thing I'm concerned about is the vectors question. But that's mainly because I did so much differential stuff studying FP3.

I'd advise everyone, in the last few moments, to go over - basic geometry, like knowing what a rhombus is, because it might come up in vectors
and some of your Core 3 integration if it's a while since you touched it, because that shows up in differential equations

GOOD LUCK!
2. I need to be in a completely different frame of mind to answer the vectors question, so I may do it first. That way it's separate from all the others
3. Would anybody be able to help me with a Jan 13 exponential models question please? It's 7)b) part 1, I'm not sure if I'm supposed to differentiate the original model or get it from somewhere else, thanks

http://www.thestudentroom.co.uk/atta...8&d=1370627149
4. (Original post by SherlockHolmes)
They are old papers which were made for AQA.

I have attached the first 3 papers and mark scheme.
Do you know where the rest of them are?
5. (Original post by Sir Lagsalot)
Do you know where the rest of them are?
http://www.mathsgeeks.co.uk/aqa.html
6. (Original post by Joeyye)
Would anybody be able to help me with a Jan 13 exponential models question please? It's 7)b) part 1, I'm not sure if I'm supposed to differentiate the original model or get it from somewhere else, thanks

http://www.thestudentroom.co.uk/atta...8&d=1370627149
Yeah you differentiate the first expression N=...
by either the qoutient rule it the chain rule. The tricky bit is getting the answer in the form they want after differentiating it

7. Is this right because in the markscheme they do it differently and so get a different value for C
http://filestore.aqa.org.uk/subjects...W-MS-JUN12.PDF

It's 8bi).
8. (Original post by littleangel9914)
Yeah you differentiate the first expression N=...
by either the qoutient rule it the chain rule. The tricky bit is getting the answer in the form they want after differentiating it
IIRC you have to work backwards from the answer that they give you to prove that it's the same. Or, at least, that's definitely the easiest way of doing it: have your differentiated N and their expression for dN meet in the middle.
9. (Original post by bugsuper)
IIRC you have to work backwards from the answer that they give you to prove that it's the same. Or, at least, that's definitely the easiest way of doing it: have your differentiated N and their expression for dN meet in the middle.

That's how I did it. Hope it make sense
10. (Original post by fizzbizz)
January 2013 was the easiest paper to date to be honest
No it wasn't. The incredibly low grade boundaries show that is was far from the easiest.
11. Are we expected to use/know the factor formulas in C4? The two books I have cover it but I've not seen any questions on them in the past few years.
12. "factor formulas"?

Do you mean like the factor theorem and remainder theorem? Because that seems to come up every paper.

If you mean the trig ones, which I suspect you do, then I don't think so, because it's not on the specification:

http://filestore.aqa.org.uk/subjects...60-W-SP-13.PDF

Check the trig section 12.4 for Core 4. It's just the double-angle formulae and the R-alpha method
13. sinA + sinB = 2sin((A+B)/2)cos((A-B)/2)

and so on.

Seems they're not in the spec which is good. It's strange because both my AQA C4 books cover them. Thanks all the same.
14. (Original post by Ravster)
sinA + sinB = 2sin((A+B)/2)cos((A-B)/2)

and so on.

Seems they're not in the spec which is good. It's strange because both my AQA C4 books cover them. Thanks all the same.
They haven't appeared on any past papers I've done.
15. On core four jan13 past paper question 5a why do you not need to integrate by parts?
16. (Original post by MedicineMann)
On core four jan13 past paper question 5a why do you not need to integrate by parts?
Integration by parts doesn't always work, if the powers that the variables are to don't cancel out nicely etc
its question 2 part c.

its solving cos x + 3 sinx = 2
in part a you get that cos x + 3sinx = (10)^1/2 cos (x-1.249)

need to find all answers in range 0 - 2 pi
18. (Original post by M^2012)
Integration by parts doesn't always work, if the powers that the variables are to don't cancel out nicely etc
So why does x(x^2+3)^1/2 integrated become p(x^2+3)^3/2?
19. (Original post by llmcc)
its question 2 part c.

its solving cos x + 3 sinx = 2
in part a you get that cos x + 3sinx = (10)^1/2 cos (x-1.249)

need to find all answers in range 0 - 2 pi
square roots are positive and negative
20. (Original post by MedicineMann)
square roots are positive and negative
but even though in part a it says R > 0 do you ignore this for part c?

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