HP 42S, DM 42 Integral

[Thomas Okken]

(02-12-2021 11:32 PM)Albert Chan Wrote:  

(02-12-2021 10:58 PM)Thomas Okken Wrote:  The fact that the actual integral is zero is causing the problem. INTEG waits for the relative error to drop below ACC, but when the true result is zero, the approximated result keeps getting smaller at the same rate as the absolute error estimate, and so the relative error doesn't get better.

More likely, integral results are bouncing around 0, thus unable to detect convergence.
In other words, all it see is noise.

You're right. Adding print statements in INTEG showing the result and the error estimate after each iteration produces this:

Code:

               INTEG "X"

-5.98921311713ᴇ-34   ***
5.98921311713ᴇ-34    ***

-1.31734759935ᴇ-33   ***
7.18426287633ᴇ-34    ***

-1.0279090934ᴇ-33    ***
 2.8943850595ᴇ-34    ***

3.55199210828ᴇ-34    ***
1.38310830422ᴇ-33    ***

2.36684546028ᴇ-34    ***
  1.185146648ᴇ-34    ***

-2.8689321452ᴇ-34    ***
5.23577760548ᴇ-34    ***

7.46276686603ᴇ-34    ***
1.03316990112ᴇ-33    ***

-2.3216434001ᴇ-34    ***
9.78441026613ᴇ-34    ***

-1.01058557743ᴇ-33   ***
7.78421237423ᴇ-34    ***

-6.08235288821ᴇ-34   ***
4.02350288611ᴇ-34    ***

-1.11859154415ᴇ-33   ***
 5.1035625533ᴇ-34    ***

-3.92290932651ᴇ-34   ***
  7.263006115ᴇ-34    ***

-6.63471685897ᴇ-35   ***
3.25943764062ᴇ-34    ***

4.65003711572ᴇ-34    ***
5.31350880161ᴇ-34    ***

5.01704822504ᴇ-34    ***
3.67011109323ᴇ-35    ***

-1.73454285248ᴇ-34   ***
6.75159107752ᴇ-34    ***