Calculating e^x-1 on classic HPs

[Gerson W. Barbosa]

(01-13-2016 06:43 PM)Dieter Wrote:  Accuracy problems have also been addressed in the mentioned 2014 thread. That's why back then I suggested another ln(1+x) method using sinh.

On the other hand a dedicated e^x–1 function is only required for ln 0,9 < x < ln 2, and here your method works fine. One might add two additional tests to check whether the argument is within these bounds or not. Which again makes the method less elegant...

Here is my plan B for the hyperbolic function approach:

Code:


001- LBL B
002- e^x
003- LSTx
004- 2
005- /
006- HYP TAN
007- *
008- LSTx
009- +
010- RTN

No additional tests required. On the HP-15C I get the same results of the HP-12C running your program, except for occasional differences of one digit in the last significant digit.
I won't post the formula here because it's very difficult to edit it in this tiny 4" screen, but it's apparent from the listing. Windows 10 refuses to start on my desktop computer. I guess the "CPU Over Voltage Error!" I've been receiving when attempting to boot has something to do with that...

Gerson