71. How can I solve linear systems of equations like the one shown below using the CAS on the hp 40gs?
Before I begin, it is important that you understand that this can only be done on the HP40G or hp 40gs, which have a CAS (Computer Algebra System), not on an HP38G, HP39G hp 39g+ or hp 39gs.
To do this you need to use the LINSOLV function in the CAS, which requires that the problem be in equation not matrix form. See the screens on the right.
Some points to note:
72. Can I use the infra-red port on my computer to communicate directly with my calculator and remove the need for a cable?
Answer:The information below is from Christoph Giesslink, the main author of the PC Emulator program (see my Utilities page ). I will simply add to it that I have spent a lot of time trying to make it work, for obvious reasons, with no success. If you manage to figure out how to do it reliably then PLEASE let the rest of us know how!
73. How do I transfer the results from a CAS calculation on an HP40G or hp 40gs to the Function aplet?
Answer:Highlight the expression which you want to transfer and then press the PLOT button. The calculator will ask which of the Function, Polar or Parametric aplets you want to transfer it to. It will then ask which of F1(X)..F0(X) (or R1 or X1,Y1) you want it put into. You have to manually tick/check the equation in the aplet before you can graph it.
Answer:The answer is both "Yes" and "No". You can SEND and RECV programs, notes, lists or matrices from an HP38G to an HP39/40G or vice versa with no problems.
But... if you SEND an aplet from an HP38G to an HP39G (or vice versa) then it will appear to succeed and will then appear in the APLET LIBRARY view of the new calculator. However, if you try to START it then you will not only find that it doesn't work, you may well find that your whole calculator will crash, losing your memory in the process. If it happens this will not cause permanent damage and all the built-in aplets will still be there but anything you have stored will be lost.
The easy solution is to use the Aplet Converter, which can be found on my Utilities Page, to convert your HP38G aplets to HP39G aplets. Of course they have to be stored on a PC before you can do this, which means you have to have a cable and the HPGComm communications program (also on my Utilities Page). If you don't have this - if all you have is an HP38G and an HP39G - then there's nothing you can do I'm afraid. You'll have to reconstruct the aplet from scratch. The Aplet Converter also only works in one direction - there's no way to convert an HP39G aplet to an HP38G aplet.
Answer:You may not have noticed but if you choose the 3 character from the SPECIAL CHARS view (see image right) then that's not what appears in the HOME view or a Note.
You'll find that what you get is a power of -1!
Why? Well it goes back to the original model, the 38G. On the 38G if you pressed (say) 4 and then the X-1 key on the keyboard what actually appeared was 4^(-1). This was a bit clumsy and Jean-Yves, the principal programmer for the 39G upgrade, decided to add a new character to the font so that the power of -1 could be shown directly. To do this he had to 'borrow' one of the other characters and change its appearance. He chose to adapt the 3 character because it was no use for anything very much. If you tried to use it to cube something it didn't work - you just got a syntax error because it was only ever intended to be used in Notes as are other chars such as ¿ or ½.
The only problem was that he must have forgotten to update the CHARS view to reflect the changed appearance and it's never been fixed in subsequent models. Oops! :-)
Answer:The following are excerpts from an HP User newsgroup. The answers were penned by various people and collected by Joe Horn in response to some very strange questions (and humorous answers) about batteries....
Question 1: When I replace my batteries I always find that the middle
one is dead but the other two still have some life in them. How can I balance
out the current drain from the batteries, so that the middle one doesn't die
Question by: Ameen
I am having trouble editing a sketch in the ADK because the Windows Paint program doesn't load up in Windows XP. Can you please tell me the directory it expects paint to be in, and the filename it is referring to?
On my computer, running Windows 98, you just edit the aplet in the ADK39, go to the Views menu/Sketch view, display the sketch you want to edit and click on the Edit button. This runs Windows Paint. Unfortunately on Windows XP they seem to have renamed the Paint progam so that the ADK tries to call the wrong program. Just go to the C:\WINDOWS\SYSTEM32 directory, make a copy of MSPAINT.EXE and then rename the copy to PBRUSH.EXE, which is what it was called prior to Windows XP. You should then find that it works.
Some relevant tips...
Serial numbers follow the pattern of... ccywwnnnnn
For example, if your serial number were SG72706543, then the unit was the
6543rd unit manufactured in Singapore during the 27th week of 1997.
The HP39G and the HP39G were released at the same time in April, 2000. The HP40G has a computer algebra system (CAS) but no infra-red. The HP39G has infra-red but no CAS. When we were designing the machine one of the programmers came up with a brilliant idea to save money. Instead of having a chip for each machine, he wanted to build just one chip that would be used for both. It would have both IR and CAS with an internal switch that would determine what calculator the chip was in and enable/disable the CAS and IR accordingly. Of course, we were concerned that there would be the chance of someone changing their machine type but he assured us that the internal switch would be encrypted and could not be broken.
So.... of course about 8 months later I was contacted by a hacker in Spain who thought he was terribly clever because he'd come up with an aplet which would change a 39G into a 40G. Sigh! I spent the next month trying to convince him not to release the aplet because I knew that if it became available the reaction of the examining bodies would not be good. Certainly in my home state of Western Australia at least. However, he was adamant that I was wrong about the likelihood of the authorities banning the HP from being used. After all, he was in his twenties and knew it all, whereas I'd only been teaching for as long as he'd been alive so what did I know? In the end he compromised in two ways. Firstly, he agreed not to announce it publicly and to make it available only if people asked for it. Secondly, he (quite cleverly) programmed the aplet, which was called the "CAS Enabler", so that if you renamed it then it no longer worked. This at least made it easy for examiners to see whether it was on the calculator simply by checking the APLET view. He also embedded a special character in the name that couldn't be accessed from the keyboard or the CHARS view. This meant that if you renamed it before an exam and then tried to change the name back afterwards you couldn't access this special character and so it still wouldn't work.
This worked for about another year. Then gradually there began to be rumours about the aplet's existence and finally it reached Western Australia via, I believe, a student who had a friend in Italy or had been on holiday there. At this point someone contacted the State Curriculum Council about it. When they asked me about it I confirmed the problem and explained the conditions the author had placed on it. Based on this they decided that the current students (year 12) who were about to do their exams would be allowed to continue to use the calculator, subject to inspection at the beginning of the exam to ensure the CAS Enabler aplet wasn't on any calculators. The same was to hold for the following year's students (year 11) but the year 10s were told that they would not be able to use the 39G in their uni entrance exams and it was now officially banned. I was told that they were originally talking about billing HP for extra examiners to check the calculators but in the end teachers did it.
As you can imagine this ban did not go down well with the students who had bought calculators at the start of year 10 and were now being told they couldn't use them. Fortunately HP had had enough warning that they had had time to bring out a replacement model, the 39g+, which had a chip in which the CAS had been completely removed. To their credit they replaced all the calculators for the year 10s in the whole state free of charge. It must have cost them a fortune! The problem was that the 39g+ had been produced in a rush and the keyboard design was outsourced to China. This proved to be a mistake. There had been occasional problems with the keyboard of the 39G/40G but the original 39g+ keyboard was terrible! A second release was done later with a much improved keyboard and any machines that gave problems were replaced under warrantee but the damage had already been considerable to HPs reputation. It was not until the release of the 39gs/40gs, which use a completely different design, that the keyboard problems were finally fixed.
If you've read this question before then you'll know that for some years now I've refusing to confirm the existence of this aplet or make it available on this site. There were a number of reasons for this. Firstly, I've signed contracts with HP that limit what information I'm allowed to discuss for 5 years after a project's release and so haven't been able to discuss it before this. Secondly, let's suppose that I had made the aplet available on this site. Since its use was clearly illegal in any examination, all I'd be doing is helping a student to cheat. Morally this is hardly a good idea. Additionally, I'd probably be laying myself open to a law suite if a student was caught and their uni career ruined as a result of having obtained the aplet from me.
In the meantime, if a teacher contacted me to ask about it then I would email them back telling them that if they requested a copy on official school letterhead then I'd send it to them. A couple of students tried to pretend that they were teachers but never got back when I told them this! I'm still not going to put it on this site and I'm only telling you all this now because I doubt if there are any students out there still using the old 39G. If you want a copy of the aplet for some reason then contact me and just convince me you're allowed to have it.
So, now you know!
Last modified: 19 Dec 2007 Sitemap Home Contact Me