Incorrect answer in indefinite integration (HP Prime) - Printable Version +- HP Forums (https://www.hpmuseum.org/forum) +-- Forum: HP Calculators (and very old HP Computers) (/forum-3.html) +--- Forum: HP Prime (/forum-5.html) +--- Thread: Incorrect answer in indefinite integration (HP Prime) (/thread-21376.html) Incorrect answer in indefinite integration (HP Prime) - ReinXXL - 02-28-2024 07:00 PM integral(ln(x+2)dx answer: x*ln(x+2)-x+2*ln(x+2)-2 why is there a -2 at the end? RE: Incorrect answer in indefinite integration (HP Prime) - rkf - 02-29-2024 08:55 AM (02-28-2024 07:00 PM)ReinXXL Wrote:  integral(ln(x+2)dx answer: x*ln(x+2)-x+2*ln(x+2)-2 why is there a -2 at the end? Why not? Indefinite integrals are always +/- any arbitrary constant value, of which "-2" is a special case. I assume this results from Xcas implementation. RE: Incorrect answer in indefinite integration (HP Prime) - lrdheat - 02-29-2024 02:25 PM I had the same thought. Was wondering how/why XCAS came up with a constant equaling 2 as opposed to something else! RE: Incorrect answer in indefinite integration (HP Prime) - KeithB - 02-29-2024 02:46 PM Maybe it is the airspeed velocity of an unladen African sparrow? RE: Incorrect answer in indefinite integration (HP Prime) - carey - 02-29-2024 03:42 PM (02-29-2024 02:46 PM)KeithB Wrote:  Maybe it is the airspeed velocity of an unladen African sparrow? And because the airspeed velocity is negative (-2), perhaps it is flying backwards :) RE: Incorrect answer in indefinite integration (HP Prime) - chromos - 02-29-2024 04:31 PM Why -2? You can rewrite the answer x*ln(x+2)-x+2*ln(x+2)-2 as (x+2)*ln(x+2)-(x+2). RE: Incorrect answer in indefinite integration (HP Prime) - Thomas Klemm - 02-29-2024 04:42 PM (02-28-2024 07:00 PM)ReinXXL Wrote:  why is there a -2 at the end? We can consider the singularity at $$x=-2$$ a natural lower bound of the definite integral. This choice of the integral constant makes it $$0$$ at that value: \begin{align} F(x) &= \int_{-2}^{x} \log(t+2) \; \mathrm{d}t \\ \\ &= (t+2) \log(t+2) - t \Big|_{-2}^x \\ \\ &= (x+2) \log(x+2) - x - 2 \\ \end{align} RE: Incorrect answer in indefinite integration (HP Prime) - toml_12953 - 02-29-2024 05:47 PM (02-29-2024 03:42 PM)carey Wrote:   (02-29-2024 02:46 PM)KeithB Wrote:  Maybe it is the airspeed velocity of an unladen African sparrow? And because the airspeed velocity is negative (-2), perhaps it is flying backwards Or flying West? RE: Incorrect answer in indefinite integration (HP Prime) - parisse - 02-29-2024 06:23 PM Not really mysterious, it's a linear change of variable.