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# C4 formula HELP Tweet

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1. C4 formula HELP

Found this in the C4 ocr spec, what does it mean and what's it for?

Any help much appreciated, exam's tomorrow!
2. Re: C4 formula HELP
I'm not familiar with that formula (I do Edexcel) but essentially what it looks like is that if you have a function x another function, and one of the functions contains the differential of the other, then it integrates like that
3. Re: C4 formula HELP
...That's a formula? I don't recognize it either..

Well, if you differentiate both sides, you get the chain rule, no?
Maybe it's some form of
4. Re: C4 formula HELP
It looks like just an application of the chain rule:

Considering that (for "nice" functions) , this then gives the formula you've quoted.

An example of a question in which it may be of use:

Spoiler:
Show
Take and .

Then use the formula.

EDIT: In fairness, though, I can't see why it'd be any easier to use this formula than to do such integrals by substitution.
Last edited by james.h; 20-06-2012 at 16:41.
5. Re: C4 formula HELP
Thanks everybody for all your help.

I think you're right and it's just a weird way of putting the chain rule. Just confused me cuz I'd never seen it before. Thanks for clearing that up.
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