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# Edexcel A2 C4 Mathematics June 2015 - Official Thread watch

1. (Original post by RobHunter97)
If you differentiate ln(6x), it becomes 6/6x which cancels to 1/x. Therefore 6x must become 6ln(x) if you integrate
Thanks, that makes sense, I had thought dy/dx of lnx was just f'(x)/ x not f'(x)/f(x).
2. (Original post by mdc96)
Hi, can anyone explain why integrating 6/x is 6lnx and not ln6x? Thanks
6/x = 6(1/x)
3. (Original post by the bear)
no... you can use integration by parts...in a cunning way
I said sensible!
How do you do it with ibp?
4. (Original post by rayquaza17)
I said sensible!
How do you do it with ibp?
am not allowed to go into details
5. (Original post by the bear)
am not allowed to go into details
Is it a secret like?
6. (Original post by rayquaza17)
Is it a secret like?
kinda
7. (Original post by rayquaza17)
I said sensible!
How do you do it with ibp?
the way you would have done a reduction formula.
8. (Original post by NikolaT)
cos(x) = cos(3x - 2x)
cos(5x) = cos(3x + 2x)

Does that help?
9. (Original post by TeeEm)
the way you would have done a reduction formula.
I knew it wouldn't be sensible.

(Not saying reduction formula isn't sensible, but it's not sensible for like n=2)
10. (Original post by rayquaza17)
I knew it wouldn't be sensible.

(Not saying reduction formula isn't sensible, but it's not sensible for like n=2)
not sensible as it is not practical...
however it is a good introduction for integrals which can only be done this way such as sec3x or excosx, tan3x etc
11. (Original post by kite0nfire)
They give similar functions when out into addition formula. Stuff cancels very nicely.

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12. (Original post by kite0nfire)
cos(3x - 2x) = cos3xcos2x + sin2xsin3x

cos(3x + 2x) = cos3xcos2x - sin2xsin3x

cos(3x - 2x) - cos(3x + 2x) = cos3xcos2x +sin2xsin3x - cos2xcos3x + sin2xsin3x

cos(3x - 2x) - cos(3x + 2x) = 2sin2xsin3x

i.e cosx - cos5x = 2sin2xsin3x

hope this helps
13. (Original post by RobHunter97)
Obviously, but I mean approximately. 50s, 60s etc.
Mid 60s should do it .

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14. Sites for hard papers?

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15. I second this. I've done all the Soloman papers in Easter holidays - just finished June 2013 which was a dream. Can anyone recommend a tough edexcel official past paper?

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16. (Original post by kite0nfire)
17. (Original post by Dante991)
I second this. I've done all the Soloman papers in Easter holidays - just finished June 2013 which was a dream. Can anyone recommend a tough edexcel official past paper?

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Do all of the below, and you're set

http://www.physicsandmathstutor.com/...rs/c4-elmwood/
18. (Original post by TeeEm)
sex3x
19. Any kind of questions you guys are feeling might come up?

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