Swiss army knife equations
12-21-2013, 11:02 AM
Post: #1
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
Swiss army knife equations
Comparing the HP-42S and (horribile dictu!) the HP-35S, the latter features something the first doesn't: equations, found top left under the label FN=. Looking at them, they seem to cover what is covered by the SOLVER of the HP-42S. Is this true or do I miss something here?

d:-?
12-21-2013, 06:21 PM (This post was last modified: 12-21-2013 06:22 PM by r. pienne.)
Post: #2
 r. pienne Member Posts: 53 Joined: Dec 2013
RE: Swiss army knife equations
On the 35s, you can store a list of equations, using the EQN key. You can evaluate/solve/integrate any of them.

You can also solve/integrate a program, by pressing the FN= key and a program label. To solve, then press the Solve key and a variable name. The calc will try to find the value of the variable so that the program returns 0 on the stack.

Page 15-1 of the 35s user manual explains it. The last paragraph of the Wikipedia article seems to sum it up quite well.

I don't know enough about the 42s to compare the two. Free42, here I come!
12-21-2013, 11:25 PM
Post: #3
 Michael de Estrada Senior Member Posts: 368 Joined: Dec 2013
RE: Swiss army knife equations
The HP 33s can do all of this as well, and it cost $20 less than the 35s when it was still being made. In fact, Chapter 14 of the HP 33s user's guide is word for word identical to Chapter 15 of the HP 35s User's Guide. It also didn't eat batteries, had direct rectangular<>polar coordinate conversions, and separate dedicated primary keys for STO and RCL. 12-22-2013, 06:24 AM Post: #4  walter b On Vacation Posts: 1,957 Joined: Dec 2013 RE: Swiss army knife equations (12-21-2013 11:25 PM)Michael de Estrada Wrote: The HP 33s can do all of this as well, ... Ok, I can also take the HP-33S for comparison if you prefer. What, however, is your answer to my question? Is EQN equivalent to the HP-42S SOLVER ? d:-/ 12-22-2013, 02:37 PM Post: #5  Dieter Senior Member Posts: 2,397 Joined: Dec 2013 RE: Swiss army knife equations (12-22-2013 06:24 AM)walter b Wrote: Is EQN equivalent to the HP-42S SOLVER ? Maybe there is a general misunderstanding. The 42s solver is able to solve an equation that is coded in a programmed subroutine, much like the 34C, 15C and 34s. However, the implementation is somewhat different and more powerful since you may define a function with multiple variables and tell the 42s solver for which one you want to have the equation solved. The 35s can do all this just as well. But on top of this it also offers another feature: The function does not have to be programmed as a subroutine, you may also enter it directly as an equation in (well, close to) textbook syntax. The 35s holds a list of equations that can be accessed and edited after pressing the EQN key. You may think of this as a separate memory space where more or less simple equations can be stored. They all may be evaluated, solved and integrated. Example - consider the pythagorean theorem: A^2 + B^2 = C^2 Press EQN and enter the formula exactly as described. It now shows up in the equation list. Assume you know A and C and you want to solve for B. Press SOLVE B and you are prompted for A and C, before the 35s returns the result for B. The 35s solver even has some built-in intelligence: if there is an easy closed-form solution it does not have to iterate, instead the solution - here B = sqrt(C^2 - A^2) - is returned immediately. Dieter 12-22-2013, 10:28 PM Post: #6  Steve Simpkin Senior Member Posts: 838 Joined: Dec 2013 RE: Swiss army knife equations (12-21-2013 11:25 PM)Michael de Estrada Wrote: The HP 33s can do all of this as well, and it cost$20 less than the 35s when it was still being made. In fact, Chapter 14 of the HP 33s user's guide is word for word identical to Chapter 15 of the HP 35s User's Guide. It also didn't eat batteries, had direct rectangular<>polar coordinate conversions, and separate dedicated primary keys for STO and RCL.

True, the 33S is a good calculator but it is so astounding ugly, I still cringe every time I pull it out of its case :/
12-23-2013, 11:33 AM
Post: #7
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: Swiss army knife equations
Dieter,
(12-22-2013 02:37 PM)Dieter Wrote:  The 42s solver is able to solve an equation that is coded in a programmed subroutine, much like the 34C, 15C and 34s. However, the implementation is somewhat different and more powerful since you may define a function with multiple variables and tell the 42s solver for which one you want to have the equation solved.

The 35s can do all this just as well. But on top of this it also offers another feature: The function does not have to be programmed as a subroutine, you may also enter it directly as an equation in (well, close to) textbook syntax.

The 35s holds a list of equations that can be accessed and edited after pressing the EQN key. You may think of this as a separate memory space where more or less simple equations can be stored. They all may be evaluated, solved and integrated.
Thanks for your explanation. So the EQN list was kind of next evolutionary step in solving equations? Does that make the HP-42S MVAR commands obsolete in a calculator featuring EQN ?

d:-)
12-23-2013, 01:33 PM
Post: #8
 Thomas Radtke Senior Member Posts: 780 Joined: Dec 2013
RE: Swiss army knife equations
(12-23-2013 11:33 AM)walter b Wrote:  So the EQN list was kind of next evolutionary step in solving equations?
No. While useful, it is in some sense a step backwards from the first implementation of an algebraic equation editor/solver in 1985 on the 18C. It had its first appearance on the 32SII and was probably designed with the limitations of the single line display and the concept of easy-to-access single letter variables in mind.

Walter, have you parted with your 35s so early?
12-23-2013, 02:20 PM
Post: #9
 Didier Lachieze Senior Member Posts: 1,508 Joined: Dec 2013
RE: Swiss army knife equations
Walter,
If you want to check the 35s solver implementation you can get the 35s emulator HERE, and the 35s User guide HERE.
Post: #10
 Michael de Estrada Senior Member Posts: 368 Joined: Dec 2013
RE: Swiss army knife equations
(12-22-2013 10:28 PM)Steve Simpkin Wrote:  True, the 33S is a good calculator but it is so astounding ugly, I still cringe every time I pull it out of its case :/

Beauty is in the eye of the beholder and function > form for nerdy engineers like myself. The new Prime is a perfect example of what happens when you allow marketing types to design a technical product.
12-23-2013, 03:26 PM
Post: #11
 RMollov Member Posts: 264 Joined: Dec 2013
RE: Swiss army knife equations
I agree HP35s has some nice features against HP42. But that is not enough given time difference. I'm also not sure which display is worse.
IMO HP41 fullnut overall is the king. Yet to be leveled. Even without the latest features.
Speed is meaningless to me. I enjoy watching the flying goose
12-23-2013, 04:09 PM
Post: #12
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: Swiss army knife equations
(12-23-2013 01:33 PM)Thomas Radtke Wrote:  Walter, have you parted with your 35s so early?
Since my HP-35S used to devour batteries I've set it on diet on my shelf where it's collecting dust now.

Anyway, I didn't use the EQN feature before. And I'm sure there are people here who (did) use their HP-42S SOLVER more than I do. I'm just wondering what's the added value of EQN to the HP-42S solving paradigm (if any).

d:-)
Post: #13
 Thomas Radtke Senior Member Posts: 780 Joined: Dec 2013
RE: Swiss army knife equations
Don't know if you would count this as added value: An equation list is easily reviewed. Trivial, isn't it?

I must admit I never sold my 35s as intended, but use it to calculate AHUs. There are some formulae for heat transfer, duct calculation and more basic thermodynamics stored in the equation editor. I'd love to use my 27S for this (multi-letter variables), but can't risk leaving a precious Pinoneer at work.

Still, this single-letter paradigm bites me when it comes to the equation editor. You should have a look at e.g. the 27S if you want to add such a feature to the 43S.
12-23-2013, 05:26 PM
Post: #14
 Dave Britten Senior Member Posts: 2,142 Joined: Dec 2013
RE: Swiss army knife equations
The equation solver in the financial line (18C, 19B/BII, 17B/BII, 95LX, 100LX, 200LX) is vastly more sophisticated than the numeric solver offered by the scientifics, though you don't get any integration capability. It will actually try to solve symbolically, so you can potentially get very quick, accurate results. You can define temporary variables within equations, check which variable is being solved for, calculate inline sums, etc. It lets you do some pretty neat tricks. I'd recommend the palmtops, or 19BII if you want this solver, since you get the usual scientific functions in addition to finance (trig being the main advantage).

If you have a 48G, or the Solve Equation Library card for the 48SX, then the multiple equation solver really takes it to the next level. You can define a set of equations that share variables, and the solver will use them all simultaneously to find the variable you're after. For example, you can define 'P=V*I' and 'V=I*R', and it will deduce how to get amps directly from current and resistance, or voltage and resistance.

I have a set of four equations that allows solving triangles: 3 forms of the law of cosines expressed for different sides/angles, and one that expresses that the three angles total 180 degrees. From that, you just punch in your known values, and it'll find the remaining sides/angles for you.
12-23-2013, 06:46 PM
Post: #15
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: Swiss army knife equations
(12-23-2013 05:15 PM)Thomas Radtke Wrote:  Don't know if you would count this as added value: An equation list is easily reviewed.
... I'd love to use my 27S for this (multi-letter variables), but can't risk leaving a precious Pinoneer at work.

Still, this single-letter paradigm bites me when it comes to the equation editor. You should have a look at e.g. the 27S if you want to add such a feature to the 43S.
Thank you for pointing to that gem. I'll blow the dust off it and try.

d:-)
12-26-2013, 05:03 PM
Post: #16
 walter b On Vacation Posts: 1,957 Joined: Dec 2013
RE: Swiss army knife equations
(12-23-2013 06:46 PM)walter b Wrote:
(12-23-2013 05:15 PM)Thomas Radtke Wrote:  You should have a look at e.g. the 27S if you want to add such a feature to the 43S.
Thank you for pointing to that gem. I'll blow the dust off it and try.
Advantage of holidays is one can let such intentions come true. I agree on the 27S featuring a very friendly and comfortable SOLVE. Equations are maintained easily.

Let's try to expand that paradigm a bit: Insisting on naming (i.e. labeling) each equation we may refer to it even in programs. So any equation of 27S-type could stand for a programmed function of 42S-type featuring MVAR steps. Sounds like a good base to start with.

d:-)
12-26-2013, 05:38 PM
Post: #17
 Massimo Gnerucci Senior Member Posts: 2,491 Joined: Dec 2013
RE: Swiss army knife equations
(12-26-2013 05:03 PM)walter b Wrote:  Let's try to expand that paradigm a bit: Insisting on naming (i.e. labeling) each equation we may refer to it even in programs. So any equation of 27S-type could stand for a programmed function of 42S-type featuring MVAR steps. Sounds like a good base to start with.

d:-)

This looks promising

Greetings,
Massimo

-+×÷ ↔ left is right and right is wrong
12-26-2013, 07:51 PM
Post: #18
 Thomas Radtke Senior Member Posts: 780 Joined: Dec 2013
RE: Swiss army knife equations
Yes, excellent idea.
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