Collection of interesting curves which can be graphed on the 38/39G.
This is now maintained on my site since Jim moved on to other interests.|
Note: this is obviously out
of date now! :-)
The HOME view stores all your calculations so that they can be re-used. This consumes quite a lot of memory. It is a good idea to clear the History regularly by pressing SHIFT CLEAR in the HOME view.
Although it is tempting to accumulate more and more notes that can be used in your various tests and exams, eventually this will cause problems with aplets. It is best to periodically dump them onto a computer using the Connectivity Kit. That way you can clear the calculator's memory if necessary without worrying about losing work. The 232Kb available in most models should be more than sufficient that this should not occur. You can store the equivalent of about 70 A4 pages of text in that amount of memory!
When you load aplets onto your calculator they often come with "attached" programs to do the work. These are stored in the Program Catalogue. Press SHIFT PROGRAM to see the list of programs currently stored on your calculator. Generally these are named so as to make it clear which aplet they belong to. For example, an aplet called TANGENT LINE might have programs called .TANG.S, .TANG.PLT, .TANG.LIN etc. To delete a program, move the highlight onto it and press DEL. Alternatively SHIFT CLEAR will delete all of them but be careful you're not deleting programs you want to keep. In case you're wondering, the program called Editline, which doesn't delete, contains a copy of whatever you last typed in the HOME view. This is so that if you hit ENTER again it can be re-executed. You can't delete this.
Other methods of clearing memory include:
In addition to these attached Notes and Sketches it is also possible to have independent Notes which are not attached to any particular aplet and which are not deleted when aplets are deleted. These are stored in the Notepad view. Press SHIFT NOTEPAD to view the contents of this Catalogue. These independent Notes can be used to store information such as formulas or study notes.
The Notepad view has its own SEND and RECV buttons, which means that these Notes can be copied from one calculator to another. See also How can I save my Notes?
When you are planning your choice of scale in PLOT SETUP it is a good idea to use multiples of this default scale. For example, rather than using -10 to 10, use -13 to 13 (double 6.5). If you need to see 0 to 20, then choose -2 to 24 instead (which is -13 to 13 moved right by 11). If you don’t like having your scale end at "nasty" numbers like 6.5 then add 0.5 to both ends, changing -6.5 to 6.5 into -6 to 7.
A really good reason for doing this can be seen if you graph the function F1(X)= Sqr-root of (9-X˛) using the scale of -3.5 to 3.5 on the x axis and the same on the y axis. If you graph this in the PLOT view you will see that the two ends of the circle nearest the x axis are missing. The same thing will happen if you graph a plain square root function. The reason for this happening with the circle is that the choice of scale means that the edges of the circle at -3 and 3 don’t fall on positions for which F1(X) is calculated. A better choice would have been -3.25 to 3.25, which is half of the default scale and thus has jump sizes of 0.05. If you try that scale you will find that you get the full half circle.Why does the default screen for the PLOT view have such a strange set of axes? If speed is important then switch on SIMULT in the second page of the PLOT SETUP view (press the screen button). This causes multiple graphs to be drawn simultaneously instead of one after the other. It's not as easy to tell which is which but it is definitely faster. The default for this setting is to be switched on; you may find that, like me, you like it better switched it off!
For example, if you were told to find the intersection of two graphs using
the Bisection method and were required to show working, then enter the first
function into F1(X), the second into F2(X) and then enter F2(X)-F1(X)
into F3(X). Now change to NUM SETUP and change 'Automatic' to ‘Build Your Own’.
Finally, change to NUM view. Enter two values for x which bracket the
intersection point (presumably you know these already or can get them from the
PLOT view). The third column contains the two function values and the difference between the two functions.
If the two values bracket the intersection, then this difference should have a positive value
for one x and a negative for the other. You can now enter further x values which
gradually zero in on the intersection to the required degree of accuracy.
Yes - it’s a pain isn’t it! On the HP38G, the MODES view only controls the HOME view. Each aplet has its own setting for angle type and numeric type and these are not inherited from the HOME view. If you are having trouble with axis labelling in the PLOT view then the simplest way to fix it is to alter the settings in PLOT SETUP to better values.
If it is particularly important to keep your current settings then (i) make sure the aplet is highlighted in the LIB view, (ii) return to the HOME view and type Fixed Format and 4 Digits. This will set the aplet numeric format to ‘Fixed 4’ but it doesn't take effect until you save the aplet under a new name (a bug in the HP38G). So now go the the LIB view and save the aplet under a new name. If you now PLOT or SHOW something within the aplet the ‘Fixed 4’ setting will be used. This doesn't affect the numeric format in the SYMB view.
This problem has been fixed on the later models by tying the MODES view to the aplet
and to HOME. This means that the settings for the aplet and the HOME view
always match and a change in the MODES view changes both. It also means
that changing aplets may result in a change to the angle and numeric settings
and this is why on the your calculator the name of the aplet always appears at the top of
the HOME view - to remind you of this possibility if you change aplets.
This is called doing a soft reset or soft reboot. Hold down the ON key and then, while holding still it down, press (and hold) the third screen key. Hold the two buttons down for a moment then release them.
When you do this you should briefly see a copyright screen and then find yourself in the HOME view with the History having been cleared. Very occasionally you'll find that you get a screen full of strange characters. Just do it again.
Note 1: There is another version of this called a hard or full reset which uses the first and sixth screen keys (HP39G users see note 2). DO NOT do this unless you are sure you don't need anything stored on the calculator! If you do it then you will find that the calculator's memory will be completely wiped, resetting it back to the default values it had when you first opened the box. Personally I do this fairly regularly anyway - it clears the system out completely. It doesn't erase the normal aplets, just resets them back to factory defaults.
Note 2: On the HP39G and later models the full reboot is a little harder to do (for increased safety). On the HP38G you just had to hold down the ON button and press the first and sixth screen keys (SK1 and SK6). On the later models you have to release SK6 first before releasing SK1 in order to reset. If you release both at once then it may still reset but it might go into diagnostic mode and the screen will fill with all sorts of strange stuff. If this has happened to you, do an ON+SK3.
Note 3: If your calculator has locked up so that the keyboard is not responding then try turning the calculator over and looking for a small hole. If you unbend a paper clip and poke it into this hole you will feel a small button which you can press (gently). This is the equivalent of doing a soft reset using ON+SK3 and you will hopefully find that this will unlock it without losing any memory. It's worth a try.
Note 4: If you press ON+SK2 instead of SK3 then you will be put into diagnostic mode. This is a mode that the engineers can use to test a faulty calculator. Feel free to experiment with it. To exit, just do an ON+SK3.
Last modified: 19 Dec 2007 Sitemap Home Contact Me