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Solver question
06-15-2014, 11:46 AM
Post: #1
Solver question
I entered in the solver-app of my HP 39gii this equation: x^2+1=0.
The numeric view of the calculator shows a real number as solution. why?
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06-15-2014, 12:39 PM (This post was last modified: 06-15-2014 12:41 PM by CosmicTruth.)
Post: #2
RE: Solver question
50G has flag 03 function -> number

Thanks
~~~~8< Art >8~~~~

PS: Please post more 50G stuff :)
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06-15-2014, 01:10 PM
Post: #3
RE: Solver question
Isn't the point for X^2 = -1, X has no real solutions Wink

I don't think a flag helps for that!

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06-15-2014, 01:12 PM
Post: #4
RE: Solver question
Thats the point, HP67: The 39gii SHOWS a real solution!!!
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06-15-2014, 01:22 PM (This post was last modified: 06-15-2014 01:26 PM by HP67.)
Post: #5
RE: Solver question
Sorry, I don't have one of those to test. Wait a bit and one of the guys from HP will answer you.

What output do you get?

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06-15-2014, 02:41 PM
Post: #6
RE: Solver question
The emulator (FW rev. 19148) shows zero and no error, but Info states that this is an extremum. The whole procedure is copious and counterintuitive imo.
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06-15-2014, 03:01 PM
Post: #7
RE: Solver question
My emulator shows also zero. Please choose 1 as start value. Again: I get a real solution. Thats curious!!!
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06-15-2014, 06:56 PM
Post: #8
RE: Solver question
It is not curious at all.

Q: Why does it show a real number?
A: Because it is a numerical solver.

The 50g does the same thing. You get a real result back, and each time you press solve it will return a slightly different number. Pressing INFO reports that it has found an extremum around that location.

TW

Although I work for the HP calculator group, the views and opinions I post here are my own.
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06-15-2014, 07:22 PM
Post: #9
RE: Solver question
In the classroom:

Teacher: What is the solution of X^2+1=0 ?
Student: 0

Teacher: Why?
Student: The calculator shows it!

Teacher: The calculator shows the wrong result.
Student: well, then ....
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06-15-2014, 09:16 PM
Post: #10
RE: Solver question
What does this have to do with the HP PRIME?

I've already seen like 4 or 5 threads about this calculator on the HP PRIME sub-forum...
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06-16-2014, 12:16 AM
Post: #11
RE: Solver question
(06-15-2014 09:16 PM)alexzkter Wrote:  What does this have to do with the HP PRIME?

Well, the 39gII was the basis for much of what exists in Prime and so this is probably the best place for it I think. In fact, for quite a while you could build one or the other by simply flipping a switch during the build process.

TW

Although I work for the HP calculator group, the views and opinions I post here are my own.
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06-16-2014, 06:16 AM (This post was last modified: 06-16-2014 09:35 AM by HP67.)
Post: #12
RE: Solver question
(06-15-2014 06:56 PM)Tim Wessman Wrote:  It is not curious at all.

Q: Why does it show a real number?
A: Because it is a numerical solver.

The 50g does the same thing. You get a real result back, and each time you press solve it will return a slightly different number. Pressing INFO reports that it has found an extremum around that location.

You lost me here. My 50g shows the correct solution(s). When COMPLEX mode is not set, the 50g shows no solutions ISOL Error: No solution found. When COMPLEX is set it shows { 'X=i*-1' 'X=i' }. Both using ISOL.

Ok, I think I understand now. The SOLVER app does produce a real (wrong) result. This is confusing. Glad I tried ISOL first or I would be disappointed now Wink

How are we supposed to use this effectively, and why doesn't it show the correct complex value for the solution like ISOL?

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06-16-2014, 08:59 AM
Post: #13
RE: Solver question
(06-16-2014 06:16 AM)HP67 Wrote:  Ok, I think I understand now. The SOLVER app does produce a real (wrong) result. This is confusing. Glad I tried ISOL first or I would been disappointed now Wink

How are we supposed to use this effectively, and why doesn't it show the correct complex value for the solution like ISOL?

I think that the HP numeric solver has always behaved like this. If there is no root but there is an extremum it returns the extremum. The HP manuals for machines with this solver all have an appendix, discussing the solver's behaviour and how to interpret the results it returns, in which this issue is mentioned.

These earlier calculators were not aimed at students, however. Students don't read manuals! The Prime pops up an error box saying "Error: extremum found" which, I think, is a good approach. If the HP 39gii ever gets an update this would be a worthwhile change.

Slightly OT: I like the Prime a lot and have showed it to my students who also like it, but they are unlikely to spend about 100 UKP on a calculator. The HP 39gii is much cheaper and still an excellent machine, but I don't feel able to recommend it to them because it still has bugs and shows no sign of being supported. If HP wants to challenge Casio in UK schools they should not neglect the lower-priced end of the market.

Nigel (UK)
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06-16-2014, 09:30 AM
Post: #14
RE: Solver question
(06-16-2014 06:16 AM)HP67 Wrote:  [...] why doesn't it show the correct complex value for the solution like ISOL?
Because the solver only works in the real domain.

(06-16-2014 08:59 AM)Nigel (UK) Wrote:  I think that the HP numeric solver has always behaved like this. If there is no root but there is an extremum it returns the extremum.
27S and relatives show the boundaries used last (left and right)
35S: NO ROOT FND
15C: Error 8
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06-16-2014, 09:34 AM (This post was last modified: 06-16-2014 10:32 AM by HP67.)
Post: #15
RE: Solver question
Yeah but the solution it shows isn't a solution and the extremum aren't helpful. I'd rather get an error like I get from ISOL when COMPLEX isn't set.

Off to read the manual...

Edit: looking quickly, I don't see anything on this in the 50g doc. This isn't my area anyway, so...

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06-16-2014, 09:36 AM (This post was last modified: 06-16-2014 09:56 AM by Thomas Radtke.)
Post: #16
RE: Solver question
(06-16-2014 08:59 AM)Nigel (UK) Wrote:  If the HP 39gii ever gets an update [...]
Last update is from end of last year, so there's hope this calculator isn't forgotten yet.

Problem (real problem!) is HPs legal departement. No way to find out if a certain calculator still has support or not. Tim won't tell. In its current state, the 39GII is of limited value IMO. There are bugs, the streamer app is ridiculous, and things like those discussed here are just terrible. There's a huge display but I have to press a softkey to find out the root isn't a root. This is not working, not even in school.
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06-16-2014, 02:45 PM
Post: #17
RE: Solver question
(06-16-2014 09:36 AM)Thomas Radtke Wrote:  the streamer app is ridiculous

How? All we get is great feedback from educators and teachers alike. I'd like to hear what is problematic.

TW

Although I work for the HP calculator group, the views and opinions I post here are my own.
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06-16-2014, 02:53 PM (This post was last modified: 06-16-2014 02:55 PM by Thomas Radtke.)
Post: #18
RE: Solver question
(06-16-2014 02:45 PM)Tim Wessman Wrote:  How? All we get is great feedback from educators and teachers alike. I'd like to hear what is problematic.
Measurements are view only apparently (plot and trace). How are the students supposed to actually work with the data? Write them down on paper and reenter them into the calculator?
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06-16-2014, 03:26 PM
Post: #19
RE: Solver question
(06-16-2014 02:53 PM)Thomas Radtke Wrote:  Measurements are view only apparently (plot and trace). How are the students supposed to actually work with the data?

Ah, makes since now.

Since I am guessing you have a Prime emulator installed, please go to the Help->Datastreamer menu to open the streamer PDF. Starting on page 17, with the "Select Data" section and then continuing with the "Export Data" and "Analyze Data" sections. This is followed by a long example showing how an experiment can be run all the way through analysis.

Summing it up though, basically you hit the EXPORT menu key (on the main menu in the plot view) once you have captured the data of interest and stopped streaming. Then you select a region or area you'd like to work with, determine how many points of that data you'd like, and then export it to the 2var stat application where the analysis continues. Alternatively, if you have an experiment that you manually collect data at a specific point by pressing a menu key in the NUM view. Alternatively, you can setup an experiment to collect for a specific length of time and interval which will automatically send the data when complete.

TW

Although I work for the HP calculator group, the views and opinions I post here are my own.
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06-16-2014, 03:38 PM
Post: #20
RE: Solver question
(06-16-2014 03:26 PM)Tim Wessman Wrote:  Since I am guessing you have a Prime emulator installed [...]
No, it was about the 39GII. The manual, online-help, and internet resources say nothing about this app. There's a video on utube for a different HP calculator/Streamer setup not showing any tools for data colection and analysis.

In addition, one user said (in another thread where you participated) the omission of data collection was kind of a missed opportunity. I asked in the same thread if this is true (kind of) but there was no reaction.

From all this, I just concluded what I wrote before. If that's not true (again, for the 39GII), the marketing departement needs to wake up and make some movies - and I have to appologize.

Anyway, thanks for your answer and the Prime informations.
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