New user frustration

[byoung]

Hello, everyone. I'm new to the Prime (and this forum), but not to HP calculators. I started with the 34C back in 1981, and progressed through the 28C, 48SX, 50g, and 17bII+. The Prime seems like a different beast, and I feel like a beginner in spite of 4 decades using RPN. Some of my frustration is not being able to duplicate what's in the manual (often I get a syntax error because I'm in the wrong mode or something). For example, the manual (under calculus - differentiate) says that the $ symbol followed by an integer can be used for multiple differentiations, so diff(f(x),x$3) should be the same as diff(f(x),x,x,x). But, I get the following results:

diff(x^4*y^4,x,x,x,y,y) = 288xy^2 which is correct. However,
diff(x^4*y^4,x$3,y$2) = 0 ???

Also, it changes the syntax from x$3 to $(x,3). Am I doing something wrong? Maybe I'm using the "wrong" $ symbol. I say this because I found a nice molar mass program on this forum and kept getting a syntax error until I discovered that the double quotes on the small menu (shift-9) are NOT the same as the ones on the char menu (shift-Vars)!

Also, have some of the old commands gone away? I can find no mention of things like ISOL and QUAD from the 28 and 48 series. So, if I have c^2 + d^2 = 1 and I want to solve symbolically for c in terms of d, is there a command on the Prime that does this? Thanks!

[goetz]

The manual may not be up to date and contain some typos.

What I found out for your examples, what you could try. Go to CAS mode first, then enter:

diff(x^4*y^4,{x,y}{3,2})

gives the desired answer for the differentiation. For solving the equation, also in CAS mode, enter the following:

zeros(c^2+d^2=1,c)

This gives the two symbolic solutions for variable c in terms of d.

If you don't get the correct results, make sure the variables (x,y,c,d) have not been assigned any values in CAS. You can check this by pushing the Vars button, then Cas->All and look into the list for these variables (should not be present there!).

[byoung]

(08-18-2022 06:42 AM)goetz Wrote:  The manual may not be up to date and contain some typos.

What I found out for your examples, what you could try. Go to CAS mode first, then enter:

diff(x^4*y^4,{x,y}{3,2})

gives the desired answer for the differentiation. For solving the equation, also in CAS mode, enter the following:

zeros(c^2+d^2=1,c)

This gives the two symbolic solutions for variable c in terms of d.

If you don't get the correct results, make sure the variables (x,y,c,d) have not been assigned any values in CAS. You can check this by pushing the Vars button, then Cas->All and look into the list for these variables (should not be present there!).

Thanks for the help. I must still have a wrong setting somewhere because the calculator keeps changing what I type. In your first example on differentiation, the braces get changed to square brackets and I get a "bad argument value" error. I made sure none of the variables exist in the CAS list. Your second example using the zeros command worked perfectly. Thanks.

[goetz]

Oops, sorry, I just noticed there was a comma missing in what I typed below. There should be a comma between both curly braces blocks:

diff(x^4*y^4,{x,y},{3,2})

Let me know if that works for you now. There are 3 arguments to this diff function here: function, variables, derivatives.

[byoung]

I had noticed the missing comma and tried it both ways with the same result. If this is working for you, I must have a wrong setting somewhere. I'm in CAS mode and using shift-8 for the curly braces. I also tried the braces from the char menu in case there was something weird like the issue with the double quotes I mentioned in my original post. The connectivity kit says I have version 20211202 v 14603 and there are no further updates available. By the way, where did you find the syntax with the curly braces? I wouldn't even know where to look for this. Thanks again.

[goetz]

I am using the Android Pro version, not a physical calculator. Unfortunately, the "firmware" is a bit older on that version (see some other discussion on this forum), and the software version does not give a clear indication, as it seems it was updated without using a newer source to build. It is version 14591, but no new features like Python. I tried my command also on the virtual calculator on Windows 10 (version 14592), and it worked.

What you may want to try: Go to the "Mem" menu (by hitting shift-mem (key)), then scroll down to Backups, to create a new backup. Then reset the calculator and see if the command works then. You should be able to restore the calcuator from the backup in the same menu later on, but I cannot guarantee, as i have never tried on a physical Prime (but it worked on the apps).

I found part of my solution in the built-in help. Just enter the "diff" command on the HP Prime command line, then hit the HELP key to see the help for diff. It shows some examples (see the example soft key!), including some with curly braces for multiple variables, and a 3rd parameter for the order. I guessed that adding a list with two numbers for both x and y would work, and it did. I found that the built-in help often helps and the examples will give an idea for some additional variants of commands. Not everything is documented, though.

The curly braces key you used (Shift-8) is the correct one, it inserts a pair of them.