Reminders/notes to help recall variable meanings in equations  Printable Version + HP Forums (https://archived.hpcalc.org/museumforum) + Forum: HP Museum Forums (https://archived.hpcalc.org/museumforum/forum1.html) + Forum: Old HP Forum Archives (https://archived.hpcalc.org/museumforum/forum2.html) + Thread: Reminders/notes to help recall variable meanings in equations (/thread211682.html) 
Reminders/notes to help recall variable meanings in equations  Chris C  02142012 Several equations I want to store in my 35s contain, when written in books, variables using the same letter with different subscripts. (See the 3rd post here for an example of what I mean: http://www.hpmuseum.org/cgisys/cgiwrap/hpmuseum/forum.cgi?read=211648#211648 ) Of course the 35s doesn't support subscripts so a letter can only be used once when storing an equation. This means other (nonmeaningful) letters must be used in the stored version of the equation. I can see this being a problem after not using one for a while (I'll forget what values go where in the equation.) I do know that setting flag 10 in a program allows prompting for variables using strings of descriptive characters. This works very well when using the equation as it is programmed, and would seem to avoid the problem described above. However, when a variable within an equation is needed to be solved for, SOLVE won't work for equations in programs unless the program uses the INPUT command to receive variables  and the INPUT command prompts for variable entry using single letters only. So, despite the usefulness of flag 10, programs that don't use INPUT can't be used when I'll need to solve for different variables within equations. When this ability is necessary I'll have to use the equation list, and the original problem in the first paragraph comes back. Is there a solution to this dilemma (other than writing a program for every way an equation can be solved) ? Or if not, is there an intuitive way to save notes somewhere to help remind me which letters represent which variables for equations in the equation list? Edit: I'm using this calculator because it's the best option on NCEES's approved calc list, so switching to another calculator isn't an option.
Edited: 14 Feb 2012, 9:44 p.m. after one or more responses were posted
Re: Reminders/notes to help recall variable meanings in equations  Allen  02142012
Quote: Perhaps I misunderstand your question? You are putting the (probably easy?) equations into your calculator so you don't have to remember them, and then making notes so you don't have to remember the variables in the equations you don't remember? At some point you'll need to remember something, right?
May I make two recommendations:
2) You might consider an upgrade to a HP 48/49/50G and write a SOLVER routine. You can capture notes along with the benefits of making a nice GUI. It takes longer to write, but in the process you'll remember it better and have a cool navigation function. The TVM SOLVER is a good example. Or Page 4 of this HP guide
Re: Reminders/notes to help recall variable meanings in equations  Chris C  02142012 I can assure you I understand the material and the equations. I think you may not understand the reason for my question. Thanks anyway.
Re: Reminders/notes to help recall variable meanings in equations  Thomas Klemm  02142012 Quote:
You may enter the original equation just above the equation to solve the problem: NC=(H1H2A)/(H1H2S)
Kind regards
Re: Reminders/notes to help recall variable meanings in equations  bill platt  02142012 That's exactly what I was going to say. It is a "dummy equation". Heck, I even put a phone number in mine once, when I didn't have a piece of paper and a pencil (how crazy!).
Re: Reminders/notes to help recall variable meanings in equations  NateB  02152012 During the execution of a program, you can display a reminder prior to INPUT.
This listing displays the program name CROSS PRODUCT and then prompts for the input of VECTOR 1. A001 LBL A
You can also use a dummy equation in the Equation List as a reminder. Example:
If you are taking the FE, I'd reccomend sticking to the more common equations used for the discipline specific portion of the exam. (e.g. If you are taking the Civil specific, I'd go with Manning's eqn, HazenWilliams, DarcyWeisbach, nominal moment capacity for concrete beams, depth of compressive stress block for concrete, etc.)
Also, knowing how to use the STAT, nCr, and nPr functions will save you a lot of time during the morning session.
Re: Reminders/notes to help recall variable meanings in equations  Chris C  02152012 This seems good. It's probably just about as good of a solution as there is. Thank you very much.
Re: Reminders/notes to help recall variable meanings in equations  Chris C  02152012 Using dummy equations as labels above equations is a good idea. I'll definitely do that. Thanks! And I am planning on taking the FE, so thanks for the headsup on using the Stat, nCr, and nPr. I'll have to look into them.
I believe, though, that using reminder text before INPUT statements in programs doesn't help when using SOLVE on equations in programs (which is why I was looking for ideas on reminders for equation variables in the equation list). Won't the SOLVE function prompt for the INPUT statement variables without showing the reminder lines first? Or am I wrong? Edited: 15 Feb 2012, 5:33 p.m.
Re: Reminders/notes to help recall variable meanings in equations  Bart (UK)  02162012 Here you go!
Program listing: LABEL STEP COMMENT Regards, Bart Edited: 16 Feb 2012, 9:25 a.m.
Re: Reminders/notes to help recall variable meanings in equations  Bart (UK)  02162012
Quote:In a program, SOLVE does not prompt for inputs unless Flag 11 is set. However, Flag 11 is default clear, and also cleared after every SOLVE operation. See chapter 15 of the manual. Thus while Flag 11 is clear, you have to write the prompts for inputs into your program (see the example for the Gas Law equation on p153). Regards, Bart Re: Reminders/notes to help recall variable meanings in equations  Chris C  02162012 Extremely cool. Thanks again, very much, Bart! I won't be able to enter it for a few days, but it is at the top of my todo list, and asap.
Re: Reminders/notes to help recall variable meanings in equations  Bart (UK)  02162012 Follow on: A001 LBL A This program would be started by "XEQ A009"
In this case I used one of the 5 user flags, but i guess other types of conditionals would work too.
Edited: 17 Feb 2012, 6:39 a.m.
