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Integration Error #1174

Open rtoy opened 3 months ago

rtoy commented 3 months ago

Imported from SourceForge on 2024-07-04 01:47:58 Created by ibluesun on 2022-05-16 22:43:00 Original: https://sourceforge.net/p/maxima/bugs/3976

integrating log(x+1) should be (x+1)*log(x+1)-x according to integration by parts rule.

Maxima adds -1 to the equation .. which is not producible either by hand .. and/or using #wolframalpha with #mathematica behind it.

Source of Error: I can also imagine that the source of error stemmed from the fact that some resources stated that ∫ln(x) dx = x ln(x) -x = x (ln(x) - 1) by getting (x+1) as the parameter for x then (x+1) ln(x+1) - (x + 1) = (x+1) ln(x+1) - x - 1 <== the error appears.

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rtoy commented 3 months ago

Imported from SourceForge on 2024-07-04 01:47:59 Created by macrakis on 2022-05-16 22:47:25 Original: https://sourceforge.net/p/maxima/bugs/3976/#9275

rtoy commented 3 months ago

Imported from SourceForge on 2024-07-04 01:48:03 Created by macrakis on 2022-05-16 22:47:25 Original: https://sourceforge.net/p/maxima/bugs/3976/#3fc4

Antiderivatives / integrals always have an arbitrary constant, usually denoted C.

That is, integrate(1,x) can be x or x+1 or x-1. All of those are correct, since D(x)=D(x+1)=D(x-1)=1.

rtoy commented 3 months ago

Imported from SourceForge on 2024-07-04 01:48:07 Created by ibluesun on 2022-05-16 23:30:15 Original: https://sourceforge.net/p/maxima/bugs/3976/#3fc4/2a0a

Thank you Stavros .. I think I should get back to work on my fundamentals again.