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Musings and comments about our common interest


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More on Equations for the HP Prime

We discussed a couple of days ago about the formula library designed by Eddie B. Shore. I have added several equations on my own - namely all the decibel-watt and decibel-voltage gain calculations, loudspeaker sensitivity; but do you have equations you want to have included?

Also, it is good practice to include the equation in the “print” area, so you know what the equation does before using the solver. Tomorrow I will post the program with this latter change - but also a couple of additional equations too.

I have found that some equations that worked in the HP17bII solver don’t work in the Prime’s. “Bad guess”, the system says. Go figure. The function is not linear by any means - it has a MIN() function, but nevertheless the variable usually searched for is outside of that MIN() function, so there should be no problem. Worthy of more investigation.

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Equation library program analyzed

I loaded Eddie Shore’s Equation program in my HP Prime, tested it, and liked it a lot. There are a couple of things that could be improved, but it would require more work. But the program is very simple and good to go through and learn how easy is to achieve things in HP Prime with simple, easy to understand programs.

Let’s go through it together, and learn a couple of things meanwhile:

EXPORT eqnlib()


// March-April 2015 EWS

// Equation Library Similar to HP 48 series

// Variables A-Z & θ are global

// Initialization

LOCAL ch,d;


(Eddie didn’t use the #pragma instruction since it wasn’t available at the time he wrote the program. I have already had some problems with it due to that - but that’s an easy fix. Just remember to place it at the very beginning of the file.

Then he initializes some local variables, that will be used for the menu choices. After that, he starts the solve app - since you could be anywhere else.)

// Choose

// Main Menu

CHOOSE(ch,”Equation Library”,





“Great Circle”,

“Angle of Incidence”,



This instruction creates a menu on the screen, gives it a title, lays down the choices, and stores the choice in the variable ch.

// 1 Geometry Loop

IF ch==1 THEN

CHOOSE(d,”Geometry”,{“Area: Circle”,

“Area: Ellipse”,

“Area: Trapezoid”,

“Volume: Sphere”,

“Volume: Cylinder”,

“Volume: Cone”,

“Surface Area: Sphere”,

“Surface Area: Cylinder”,

“Distance of 2 Points”,

“Regular Polygon: Σ Angles”,

“Area: Regular Polygon”});


Then, choice after choice on menu 1, he does the same thing, but with a level two menu: you choose the equations you will use. Again, the choice is stored in a variable: d in this case. if clicked out of the menu, or escaped, you get zero and you’re out of the program.

// 1.1 Area: Circle

IF d==1 THEN



PRINT(“A = Area”);

PRINT(“R = Radius”);


Choice per choice, he stores the equation in the system variable E1 (which is the first equation in the solver). Then, prints on the screen the variables used. These will disappear when you click any key; and then you’re left with the solver. (Here is one of the improvements that could be done: we could print the formula after the variables used. I’ll do it on Monday night, when I have some time.

// 1.11 Area: Regular Polygon

IF d==11 THEN



PRINT(“A = Area”);

PRINT(“N = Number of Sides”);

PRINT(“S = Length of a Side”);


// Close out Geometry Loop


Let’s not forget this last end, to close the Geometry chapter loop!!

Finalizing, we have these two instructions, to display the solver using the formula we have set in E1:

// Display Solver




Check(1) selects the first formula in the current app, which is the solver. (Check(2) w ould have checked the second, and so on)



Starts a view of the current app. Redraw, is optional; if Redraw, is true (non 0), it will force a refresh for the view.

The view numbers are as follows:




3=Symbolic Setup

4=Plot Setup

5=Numeric Setup

6=App Info

7=Views key


Did you learn anything? I did.

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Equation library for the HP Prime

If there is a problem with the HP Prime, it is the lack of software available for it for the different professional fields: finance, engineering, physics, etc. The calculator, while extremely powerful, and programmable in a much more user-friendly language than the elegant but complicated RPL, was intended for secondary education, with extension to university maths, due to its extensive CAS system. However, if you wanted to load a formula for any physics or engineering problem, you were out of luck - they had not been programmed before.

I have tried to put together some account sets in the solver app - but I am limited to 10 for each app I set for it; and the selection of functions, and its use, could be clearly improved.

I am now excited, since I have seen exactly what I was looking for. Eddie B. Shore has created an equation library with 47 different equations that can be loaded in the solver app, covering many categories:

  • Geometry (areas, volumes, surface areas),
  • Finance (monthly loans, sales tax, break-even),
  • Temperature Conversion (Fahrenheit to and from Celsius),
  • Physics: Problems of Motion (linear distance, circular motion, pendulums, terminal & escape velocity),
  • Sound (speed of sound, Doppler effect, loudness),
  • Optics (Lens and Snell equations, spherical refraction),
  • Electronics (2 resistors series and parallel, thermal noise, Ohm’s Law),
  • Astronomy (parallax, luminosity, Kepler’s 3rd Law, time dilation),
  • Great Circle Calculations,
  • Angle of Incidence Calculations,
  • Gases (Ideal and Boyle’s Gas Laws, heat capacity, air density, isothermal expansion), and
  • Fluids (depth pressure, fluid flow, Bernoulli’s Equation).

I am now traveling, but I really look forward to get into my computer and load it in my Prime!

You can find the file with the program here:

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Function library in the HP Prime - very similar to the HP50g's

One of the things that I was missing of the HP50g in the HP Prime is the ability to keep many functions available for solving - something like the function library.

One alternative is to create multiple copies of a solver app - each with a different function. This is not good for organizing your functions!

Another alternative is to enter them into variables - but then you need to have a very good memory to know what each variable does.

But there is a “proper” solution too. Eddie W. Shore (whose blog we have mentioned many times before) has created a free application that handles 47 well used functions. You just run the app, and then choose among the different functions. These are stored in variable E1, and prior to that, you get a description of what each component of the function does.

You can find and download the application here:


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More about the Multi-Language software for the HP50g

I have received today a message from Andreas Moeller, an innovative programmer, and author of a set of tools for the HP50g.These tools include a full translation of menus, flags, and applications to the language of your choice, and an equation tree builder which is extremely useful for those that have several equations and several subdirectories in their HP50g.

(by the way, a disclaimer - we sell the HP50g with the multilanguage as a pack - and we include with it an SD card)

Andreas has been working to make its software known. We have a difficulty here: it is hard to convince a student to pay for something when he is accustomed to get everything for free - and students make 95% of all purchases of HP50g. (users are more varied - eventually the student earns his grade and starts working, keeping his calculator with him). One way he has trie is creating some videos that explain how the software works.

Here is the example about the multilanguage pack:



Equation Tree Builder

I am enjoying the full set of tools in my HP50g. It is saving lots of time in my work. When I need to find where is the nice equation that I wrote 6 months ago (how did I name the equation? What did the variables mean? Under which assumptions does the equation work?

Here is a video that shows how the tree browser is used



You can even organize your own sets of equations and transform them into programs, or even libraries, to be distributed to your friends and colleagues. Here is a video that shows how:



All in all, an excellent software, and for me (in particular the treebuilder), verging on the indispensable. Highly recommended !!

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