## Negative Cube Roots

Discussion about the new DM41X calculator
Weegie
Posts: 7
Joined: Wed Jun 09, 2021 10:28 pm

### Negative Cube Roots

First post here and only had my DM41X a week or so. Many years ago I used the HP41C in my latter college years and with my first "professional" (although I've never considered myself a professional anything). The screen eventually gave up, I really missed that calculator.

Loving the DM41 with the beautiful display and HP41 emulation it's fantastic.

Now got a DM42 on order and been trawling around watching videos and visiting blogs, forums etc: and came across this video on cube roots on the DM42 (bear with me please).

https://youtu.be/iNR7kcA08As

I thought I'd try the cube root problem on the 41 and get DATA ERROR so I tried the HP41 emulator on my computer, same result.

After all that time I never knew this was a limitation on the 41 obviously a HP limitation than a Swiss Micros problem.

I'd love to hear more from the knowledgable who are on here and will have known about this probably forever.

I'm no mathematician and a lot of the info on here is waaaay above my head.

Having a lot of fun learning though, it just intrigued me, that's all
Weegie
Posts: 7
Joined: Wed Jun 09, 2021 10:28 pm

### Re: Negative Cube Roots

Just as I posted this it struck me if the DATA ERROR is related to the 41 not natively handling complex numbers (or I don't think it can without programming). Perhaps it sees the first root as complex and can't return the value.

Of course I could be talking complete rubbish
grsbanks
Posts: 1122
Joined: Tue Apr 25, 2017 11:23 am
Location: Preston, Lancs, UK
Contact:

### Re: Negative Cube Roots

It calculates the $$n$$th root of $$x$$ by computing $$e^{ln(x)/n}$$

If $$x$$ is negative, it can't calculate $$ln(x)$$, hence the "DATA ERROR".
There are only 10 kinds of people in the world: those who understand binary and those who do not.
Weegie
Posts: 7
Joined: Wed Jun 09, 2021 10:28 pm

### Re: Negative Cube Roots

Thanks for explaining, appreciated

So finding negative roots isn't possible with the 41.

On the video I tried the test on a 48GX using the "raise to a power" to find the cube root and it returned the same answer as the DM42, but using the root finder on the 48GX returned -2.

Don't know if thats due to rounding error or if the root finder uses a different method to evaluate the root

I think I'll just try and stay clear of negative roots
Dan Simpson
Posts: 72
Joined: Wed Mar 18, 2020 3:29 pm
Location: Arizona

### Re: Negative Cube Roots

Angel Martin's SandMath 4x4 Module has an x-th root of y function that allows for negative numbers.
No DM41X should be without it!

https://technical.swissmicros.com/dm41x ... Latest.zip

Manual:
http://www.systemyde.com/pdf/SANDMATH_44_4x4_Manual.pdf
My Spirit animal is a Basset Hound.
My Collection: HP-55, HP-67 (Teenix Mod), HP-15C, HP-16C, HP-41CV, HP-41CX, SY41-CL (x2), DM41X (Beta), DM42, HP-42S, HP-48G, HP-71B (x2), HP-75C, HP-150.
Weegie
Posts: 7
Joined: Wed Jun 09, 2021 10:28 pm

### Re: Negative Cube Roots

Wow Dan

I just opened that zip, that contains a lot of modules.

Thankyou for the link to both the mod files and the documentation, I'm still trying to find my way around

The help is very much appreciated

John