Editing Talk:1201: Integration by Parts
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: Exactly; he omits the final step part of the process: ∫udv= uv - ∫vdu. This is only helpful if you can easily obtain v from ∫dv and can integrate ∫vdu . The key trick is picking u and dv properly; it's rarely as easy as saying u = f(x) and v=g(x)dx. So the joke is that he's treating integration by parts as if it's a "magic rule" on the order of the product rule for differentiation, when it's not. [[Special:Contributions/66.202.132.250|66.202.132.250]] 21:10, 19 April 2013 (UTC) | : Exactly; he omits the final step part of the process: ∫udv= uv - ∫vdu. This is only helpful if you can easily obtain v from ∫dv and can integrate ∫vdu . The key trick is picking u and dv properly; it's rarely as easy as saying u = f(x) and v=g(x)dx. So the joke is that he's treating integration by parts as if it's a "magic rule" on the order of the product rule for differentiation, when it's not. [[Special:Contributions/66.202.132.250|66.202.132.250]] 21:10, 19 April 2013 (UTC) | ||
:: I think this is it. It's funny because the described conversation happens universally every time someone who's not a full-blown math teacher tries to explain IBP to someone else. You just sort of hit this humiliating brick wall if you haven't comprehensively studied it. I'd also like to point out if u = v = x then dv = dx, f(x) = x, g(x) = 1 and your original integral was just ∫x dx to begin with (you wouldn't need IBP in the first place). [[User:Echo Seven|Echo Seven]] ([[User talk:Echo Seven|talk]]) 01:48, 21 April 2013 (UTC) | :: I think this is it. It's funny because the described conversation happens universally every time someone who's not a full-blown math teacher tries to explain IBP to someone else. You just sort of hit this humiliating brick wall if you haven't comprehensively studied it. I'd also like to point out if u = v = x then dv = dx, f(x) = x, g(x) = 1 and your original integral was just ∫x dx to begin with (you wouldn't need IBP in the first place). [[User:Echo Seven|Echo Seven]] ([[User talk:Echo Seven|talk]]) 01:48, 21 April 2013 (UTC) | ||
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Not the full explanation?But what exactly is the joke here?It takes a lot of practice to be able to do integration sums correctly.[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 05:26, 19 April 2013 (UTC) | Not the full explanation?But what exactly is the joke here?It takes a lot of practice to be able to do integration sums correctly.[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 05:26, 19 April 2013 (UTC) | ||
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:I personally prefer (1/2)x^2 - C^2 because we can use the difference of squares factorization. [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 19:41, 24 April 2013 (UTC) | :I personally prefer (1/2)x^2 - C^2 because we can use the difference of squares factorization. [[User:Alpha|Alpha]] ([[User talk:Alpha|talk]]) 19:41, 24 April 2013 (UTC) | ||
::Sure, but if you square the (variable) constant, then any result like (1/2)x^2+2 is impossible. Unless you really like complex numbers, of course - but most integration is done for functions which have "real" x. So the variant "(1/2)x^2-C" is "more correct" for the majority of people ;-) {{unsigned ip|91.89.211.18}} | ::Sure, but if you square the (variable) constant, then any result like (1/2)x^2+2 is impossible. Unless you really like complex numbers, of course - but most integration is done for functions which have "real" x. So the variant "(1/2)x^2-C" is "more correct" for the majority of people ;-) {{unsigned ip|91.89.211.18}} | ||
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:as an altruistic individual, for everyone learning integration by parts, please look up both LIATE and tabular integration. You'll thank me later. [[Special:Contributions/99.20.64.64|99.20.64.64]] 23:10, 5 May 2013 (UTC) | :as an altruistic individual, for everyone learning integration by parts, please look up both LIATE and tabular integration. You'll thank me later. [[Special:Contributions/99.20.64.64|99.20.64.64]] 23:10, 5 May 2013 (UTC) | ||
::Is is ILATE,(as I learned it).[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 12:54, 7 July 2013 (UTC) | ::Is is ILATE,(as I learned it).[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 12:54, 7 July 2013 (UTC) | ||
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