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Apr
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comment Integrating a product, one factor a derivative
Oh, damn it. Yes, it is clear now. Of course $du$ IS the derivative of $u$. But thank you both for pushing my thoughts in the right direction!
Apr
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comment Integrating a product, one factor a derivative
Yes, my problem is especially the $du=\cos t dt$. I don't see why you can do that. A good example of my problem would probably be: Given this ridiculous stupid integral $\int sin(x) \frac{1}{x^2} ln(x)\,dx$. Lets substitute $u = sin(x)$ and $du = \frac{1}{x^2} ln(x)\,dx$. Sweet, now we have $\int u\,du = u^2 + C = sin(x)^2 + C$. Obviously this is wrong, but I don't see the difference to the equation from my question.
Apr
9
comment Integrating a product, one factor a derivative
Thanks a lot for the answer! But as I said in the comment to the other answer, I just don't understand why you are allowed to substitute like this.
Apr
9
accepted Integrating a product, one factor a derivative
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awarded Scholar
Apr
9
comment Integrating a product, one factor a derivative
Ah, indeed, there was a mistake in my integration by parts. That cleared a lot up. But it looks pretty clumsy compared to the substitution. But my problem still remains: I don't see why you can substitute like you, the other answerer or wolframalpha does. I have especially a problem accepting that you can set $du = x'(t)\,dt$. Is this some fundamental thing about integrals I haven't understood? Do I just have to accept, that you can do a "string-wise" substitution like that?
Apr
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awarded Editor
Apr
9
comment Integrating a product, one factor a derivative
Oh, yes, sorry. I corrected it. x at time t is meant by x(t).
Apr
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revised Integrating a product, one factor a derivative
added 2 characters in body
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9
asked Integrating a product, one factor a derivative
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30
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answered CDI interface-based bean in JSF
Mar
30
comment CoreData inserting and immediate delete: memory usage grows and grows
I'm trying to get some useful information from the profiler, but I don't really know what I should look for. I'm looking at Statistics->Object Summary The two most memory consuming entries there are Malloc 32 Bytes and __NSArrayM. If I click the arrow right next the names I get a listing where they were created?! By far the most callers is NSManagedObjectContext. For the third entry it is NSUndoManager. Would screenshots be helpful, or should I archive the project and upload it?
Mar
30
comment CoreData inserting and immediate delete: memory usage grows and grows
Thanks for the quick answer. Ok I added autorelease, but this doesn't make any difference. I also tried calling release right before the sleep command, but this has also no effect on the memory usage. I'm a bit confused about how ARC handles the memory. I have lots of experience in many programming languages, but am pretty new to objective c, and its even more confusing that the docs you read are all written for different memory handling approaches. But as far as I understood it, you don't have to call any (auto)release statements when using ARC? Is that right?
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