HP 15C and INT(1/√(1-x),0,1)

[Dieter]

(11-26-2017 07:51 PM)salvomic Wrote:  With this code:

Code:


00 LBL 1
01 CHS
02 ENTER
03 1
04 +
05 ENTER
06 SQRT
07 1/x
08 RTN

What are the two ENTERs supposed to do?
They are not required.

(11-26-2017 07:51 PM)salvomic Wrote:  then 0 ENTER 1, f ∫ 1

What display setting do you use here?
Remember, this setting directly influences the accuracy of the result – and thus the execution time.

Code:

01 LBL 1
02 CHS
03 1
04 +
05 SQRT
06 1/x
07 RTN

Set FIX 4, and the official HP emulator returns 1,9999 almost immediately.
FIX 6 already causes the emulator to run for a while... until it stops with Error 0.

(11-26-2017 07:51 PM)salvomic Wrote:  I wonder:
1. Is there a better way to get it in hardware HP15C?
2. Why the result in emulator is not 2?

Answers to both questions can be found in the 15C Advanced Functions Handbook which explains the Integrate function in detail. Take a look at the graph near x=1 and you'll see why this integrand is not trivial and why you should not expect a plain 2. As x approaches 1 the function approaches infinity. The AFH shows how such cases can be handled.

It's always a good idea to start with a moderate display setting like SCI 2 or FIX 2 or maybe FIX 4. Higher settings may cause very long integration times, especially on a hardware 15C.

Dieter