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February 03, 2026, 12:15:43 am

Author Topic: HOW TO: Anti derivatives through derivatives.  (Read 3574 times)  Share 

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trinon

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HOW TO: Anti derivatives through derivatives.
« on: November 06, 2008, 01:44:37 am »
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Ever have an equation you want to derive, but couldn't because you plain don't know how? Well than this is the guide for you!

As a side note, this is actually covered under the Methods study design and a question like this will most probably be asked on either of the two exams.

So without further Apu (hehe, Simpsons related joke):

TRINON'S GUIDE TO ANTI-DERIVATIVES THROUGH DERIVATIVES

I'm only going to run through the fundamental method, because there isn't much else to it. It only starts getting hard in Specialist Maths when they start throwing things like differentiate and hence anti-differentiate and things like that.

We start off with an equation that we can't anti differentiate with any method that has been covered in the methods study design.



We first multiply this equation by so that we get .

Next we find the derivative via the product rule:



Next we re-arrange the new equation:



If we now anti-derive both sides we get:





Now you can Anti-derive the in-anti-derivable!

Hope this helps guys. If you've got any questions just ask.
« Last Edit: November 06, 2008, 01:56:59 am by trinon »
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Glockmeister

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #1 on: November 06, 2008, 01:49:12 am »
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Nice... didn't know about this actually
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Collin Li

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #2 on: November 06, 2008, 01:53:21 am »
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BTW, you cannot get asked to do something like this unless they provide you with the necessary function to derive first, then hence, using that result, anti-derive it to solve the more difficult integral.

Mao

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #3 on: November 06, 2008, 02:23:54 am »
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things like , and other assorted don't work with this. :P
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trinon

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #4 on: November 06, 2008, 03:03:49 am »
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things like , and other assorted don't work with this. :P

Yeah, we know. This was more for the "Differentiate and hence anti-differentiate ". It's not a perfect solution..
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dcc

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #5 on: November 06, 2008, 09:14:15 am »
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things like , and other assorted don't work with this. :P



 

And so on :P

onlyfknhuman

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #6 on: November 06, 2008, 10:00:05 am »
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Holy kcuf genius ! thanks
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BiG DaN

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #7 on: November 06, 2008, 11:01:22 am »
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this is just antidifferentiation by recognition yeh?
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excal

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #8 on: November 06, 2008, 11:14:52 am »
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Also, you can use \cos{x} to represent
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trinon

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #9 on: November 06, 2008, 11:22:32 am »
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Also, you can use \cos{x} to represent

I prefer brackets, it gives exactly what you're doing rather than "Hmm, do I include that in the cos or don't I?" dilemma.
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Mao

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #10 on: November 06, 2008, 11:44:08 am »
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Also, you can use \cos{x} to represent

I prefer brackets, it gives exactly what you're doing rather than "Hmm, do I include that in the cos or don't I?" dilemma.

no, as in non-italic and as opposed to
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trinon

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #11 on: November 06, 2008, 11:45:50 am »
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Also, you can use \cos{x} to represent

I prefer brackets, it gives exactly what you're doing rather than "Hmm, do I include that in the cos or don't I?" dilemma.

no, as in non-italic and as opposed to

I fail to care either way. Makes no difference to me.
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Cthulhu

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #12 on: November 06, 2008, 11:59:53 am »
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cos is cos and log is log, who cares? Thanks trinon :D

excal

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #13 on: November 06, 2008, 12:03:37 pm »
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Also, you can use \cos{x} to represent

I prefer brackets, it gives exactly what you're doing rather than "Hmm, do I include that in the cos or don't I?" dilemma.

Then \cos{(x)} (as Mao just used).
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Alice

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Re: HOW TO: Anti derivatives through derivatives.
« Reply #14 on: November 06, 2008, 01:36:03 pm »
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can I ask a question?   

find d/dx  2xsin3x    and hence find the exact value of    anti (x cos3x )dx 


 upper limit :pai/6      lower limit 0

thank you