+- 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: Integral with Gamma-function does not work (/thread-20866.html)
Integral with Gamma-function does not work - rawi - 11-20-2023 07:35 PM
I tried to integrate ln(X)*Gamma(X) from 0.2 to 0.8 in Home mode.
The function to integrate was (LN(X)*(X-1)!).
You can get the result for X = 0.2: -7.38868
For X = 0.5: -1,22857
For X = 0.8: -0.25979
You can graph the function which is totally smooth.
But if you try to integrate the function from 0.2 to 0.8 you get "Fehler: Ungültige Eingabe" ("Error: Invalid Input").
If I integrate only the function (X-1)! from 0.2 to 0.8 it works. Result is 1.245887.
I work with Software version 2.1.14730, Hardwareversion D, CAS-version 1.5.0.
Any idea why LN(X)*(X-1)! cannot be integrated?
RE: Integral with Gamma-function does not work - parisse - 11-20-2023 07:52 PM
It seems it is a conversion problem between Home and CAS. Inside the debugger, I can see that the postfixed ! (factorial) function is wrongly translated to a prefixed ! function (perhaps the not function)
ln(X)*!(X)
The same integral is correctly evaled inside CAS.
RE: Integral with Gamma-function does not work - rawi - 11-20-2023 11:43 PM
Thank you Parisse.
Yes, in CAS mode it works. This being a purely numerical problem I did not think of using CAS mode.
It seems it has something to do with the LN function as well. If I make the integral from 0.2 to 0.8 of SIN(X) * (X-1)! using RAD in Home mode I get the result 0.514558. This works as well in CAS mode.