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# Pleased, not Exasperated

07-08-2019 07:00 AM

I am very pleased.

Kudos to Paul on the Help Desk. He told me to Reset my calculator by pressing On, Apps, and Esc together. That wipes memory and set the calculator to its default conditions. I did that, and now all my problems are gone, except one. "implicit_diff()" now works on anything you throw at it, and I can divide polynomials symbolically and get right answers, without "bad argument" error.

Only plotting the ACOT and ASEC remain as problems I'm aware of. Surely someone out there has a HPPGC who can confirm or deny my results. Try this:

Function app, Home view. Symb x page.

Set F1(X) = ACOT(X)

Set F2(X) = dF1(X)/dX=X (chose the derivative template)

Set F3(X) = -1/(1+X^2)

F3 is the formula Calculus textbooks give for the derivative of ACOT(X). When plotted, F2 and F3 should be identical. Not the result I get. F1 is a curve approaching the x-axis asymptotically, F2 is constant for all X at -0.5, and F3 shows what the derivative should look like.

Similar comments apply for ASEC(X).

F3 is 1/|X|*SQR(1-X^2)

F2 and F3 look sort of similar, but for X=1.2, F2=2.272, and F3=0.537.

The same results occur with the emulator.

The other Trig Arc-functions plot correctly with F2 and F3 identical.

It's a backwater problem. Not many of us have occasion to use ACOT or ASEC. So, all in all, Kudos to HP for a fine calculator

Solved! Go to Solution.

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## Pleased, not Exasperated

07-08-2019 11:20 AM - edited 07-11-2019 03:14 AM

Did you try and purge the variables before trying the reset?

As I explained in a reply to one of your other posts here:

https://h30434.www3.hp.com/t5/Windows/HP-Prime-Emulator/m-p/7163271#M24894

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## Pleased, not Exasperated

07-11-2019 08:06 AM

Yes. Purging variables restored "implicit_diff()" to proper operation after using its symbolic result to evaluate the derivative for a specific x, and y. Putting values in x and y to evaluate the symbolic result requires Purge ing x and y to get the command to work right. It's good to know about purge.

But Purge in CAS view does nothing for dividing polynomials in Home view.

I have no idea how my calculator got screwed up.

But the 3 finger salute (On, Apps, Esc) corrected it.

I'm pleased. Most everything works as described in the on-board Help and User Guide. Its good to know about the 3 finger salute. But only the Help Desk knows about it. I couldn't find it in either source mentioned.

Now. If they would only correct the plot for the derivatives of ACOT(X), and ASEC(X) all would be Pirmeo.

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## Pleased, not Exasperated

07-11-2019 09:07 AM

Hi,

I was referring to CAS, as symbolic work should be done in CAS. Home is better for numerical work.

Upper case variables are default HOME variables and lower case variables are default CAS variables.

You can recall a HOME variable in CAS by using ALPHA then SHIFT then Var_name to make it upper case.

Similarly You can recall a CAS variable in HOME by using ALPHA then SHIFT then Var_name to make it lower case.

The HOME upper case variables A...Z can only take numerical values, they default to 0. You cannot use purge to reset variables A..Z, just store 0 in them.

The CAS lower case variables a..z can store expressions as demonstarted in my other post. To reset them to "nothing" you need to use purge( ).

Whenever you want to do symbolic work, I suggest to do it in CAS view and use lower case variables (which need to be purged if you do not wish substitution to take place).

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## Pleased, not Exasperated

07-11-2019 09:54 AM

Okay my error. You cand divide polynomials in Hove view.

But, out of the box, I couldn't divide polynomials unless I entered the coefficients as lists.

The 3 finger salute fixed it. (On, Apps, ESC) good to now

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## Pleased, not Exasperated

07-11-2019 10:42 AM

Yes, ON_APPS_ESC is good to know but a rather extreme as it clears all user data.

Imagine some time in the future you have several programs and/or lots of data in various apps and you are not in a position to back up to a some other device ...

By the way my post above is only an intro to Prime variables, see section 24 of the manual for many others.

In previous posts and communications I referenced another forum.

A sticky thread there is "HP-Prime: Documentation & Tutorials" in which:

0.19) How to reset the Prime to recover from some unwanted issues (All Firmware releases including 7820), by Tim Wessman

Warning: these procedures will wipe the user's work.

Make sure you have a backup (Use the Connectivity Kit for that).

a) First approach - Wipe out all memory:

Press ON-APPS-ESC (all 3 together) and release.

b) Second approach - (I will leave this for the reader to find and use at own risk)

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