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# Edexcel C3 (20/06) Revision Thread watch

1. I have only done the mock paper and it wasnt bad.

But i have not done the specimen paper though.

Anyone have it?
2. (Original post by goku999)
I have only done the mock paper and it wasnt bad.

But i have not done the specimen paper though.

Anyone have it?
http://www.edexcel.org.uk/VirtualCon...r_MkScheme.pdf
3. Thx, since there was no C3 exam in the past, i think the C3 exam 2 moro will be very similar to the mark scheme and the mock paper.
hope it is going to be easy.
4. Check out Edexcel's practice papers as well (they're abit harder).
5. hav u got a link for the mock n practice papers?
6. See first post of this thread.
7. k ty
8. Given that y = lnsecx, -90 < x <= 0, use the substitution u = secx, or otherwsie, to show that dy/dx = tanx

What I have I done wrong here, it seems simple enough unless I've made a massive error I haven't noticed?

y = lnu
dy/du = 1/u
dy/dx = 1/secx
dy/dx = cosx

9. i think that's c4
10. You can't just change the dy/du into dy/dx like that. Up to dy/du = 1/u, it's fine.

Now use chain rule:

dy/dx = (dy/du)(du/dx)

dy/du = 1/u = 1/secx
du/dx = secxtanx

=> dy/dx = (1/secx)(secxtanx) = tanx
11. Okay thanks
12. What paper is that from ntrik?
13. Its the 'Exam Style Paper' in the Heinemann C3 for Edexcel textbook.
14. anyone got the markscheme for the mock paper?
15. 2 sin x - 3 cos x in the form of R sin (x-a)

2sinx - 3cosx = Rsin(x-a)
=R[sinxcosa - sinacosx]
=Rsinxcosa - Rsinacosx

Therefore,
2sinx ≡ Rcosa
3cosx ≡ Rsina

So R = √2² + 3² = √13
a = arctan 3/2
16. Does anyone find that implicit differentiation is a much better calculus method then the whole quotent rule, chain rule turn by turn rubbish?
17. Yep. But ill probs still use the quotient/chain rubbish
18. i'll use implicit for c4 as i want the method marks for c3, implicit should be in c3 imo, it's probably the easiest topic in c4.
19. (Original post by nas7232)
i'll use implicit for c4 as i want the method marks for c3, implicit should be in c3 imo, it's probably the easiest topic in c4.
No.. Binomial expansion is

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