Bug in fsolve() or just wrong used?

07092015, 08:20 PM
(This post was last modified: 08092015 03:00 PM by KonradM.)
Post: #1




Bug in fsolve() or just wrong used?
Hello, I bougt a HP Prime calculator on Amazon. Unfortunately it is not here yet, but I got the emulator to get used to it. I like the emulator pretty much and hope the calculator will get here fast, I can't wait .
Well, I guess I found a bug in the CAS. I have not found any information about this bug somewhere else so I am not sure if it is a bug or if I am using the calculator wrong. Using the fsolve() function I was trying to find some intersections. Then I wanted to see how far I could go. So I entered some pointless equations. What I endet up was: fsolve(SIN(x)=0.05*x+1,x,(50)..50) The results seemed to be fine. The problem I found out occurs when I enter bigger ranges. For example: fsolve(SIN(x)=0.05*x+1,x,(200)..100) It doesn't give me all intersections. Using this line I get all the intersections. fsolve(SIN(x)=0.05*x+1,x,(200)..200) So the output of the calculator varies if I enter to big ranges. If the range is to big I only get one result. It doesn't seem to set limitations. I hope someone can help me. The calculator is selled since 2013 and Updated frequently. So I guess HP is working still on it aren't they? I heard about some other bugs which are fixed mostly. Is there somewhere some information from HP about future updates? Sorry if my english skills aren't perfekt. I hope didn't made that much mistakes .  Edit: So I got my calculator today. This issue still occurs on the hardware. Greetings 

01112015, 05:54 PM
Post: #2




RE: Bug in fsolve() or just wrong used?
I don't think its a bug but an inherent problem of iterative solvers in general: the range in which your solutions lie is "fixed" while you continously increase the "search range".
That is why you can define the algorithm and the variables, how iteration works (in the CASSettings, Page 2). Though I think this is a classical "Layer 8 Problem": If you look at the function, you see, that there is only a certain range where the solution may lie.... 

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