Is there a program where you type in equations and change only variables?

[GeorgeOfTheJungle]

https://www.desmos.com/calculator/izrcjwqp8i

There's a very nice "graphing calculator" app too, for Macs, PCs and mobiles.

[Beamin]

If it involves math, Matlab is the answer.  They have a 'personal' license so it's not terribly expensive.  I really like the optional Simulink package.  It includes blocks for creating analog simulations identical in concept to an analog computer.  Very cool!

Fortran - I'm an old time Fortran programmer and I write a lot of demo code to show my grandson how to do various math operations like we did it in the good old days.  Simple things, like Riemann Sums are so easy to demonstrate with Fortran (or any other language).

Desmos.com - absolutely ideal for graphing functions.  This comes up a LOT in working through his Calculus program.

Symbolab.com - if you want to see how to solve math problems, this is the place.  If you subscribe, you can get more detailed solutions but it isn't necessary.

Python and it's numeric libraries - This is the modern way to do math.  Alas, I'm going to stick with Fortran.  Buy books related to Python and Math to get specific help.

I would use fortran but my six foot tall 400lbs tape drive needs new clutches.



I thought LibreOffice was really good and had lots of support as its the Linux version of word. I have a copy of office 200X on CD; before they started doing this ridiculous monthly cloud service/payments. I use office twice a month I can't afford a monthly charge that never ends. Best way to go broke is to set up monthly payments for a whole bunch of little things.

[Ducttape]

The advantage was you could specify some of the input and output values, and it would solve for the unknowns. In other words, it was up to you which variables were inputs and which were outputs, and you could easily reclassify them.

Brilliant program for solving sets of simultaneous equations. Essentially you type in an equation on the equation sheet and when you hit 'enter' the variable sheet immediately lists all of the variables in your equation. And on each variable's line there are columns labeled 'input' and 'output'. Enter another equation and any additional variables used are now added to the variable sheet. Any variable values you know you simply add to the input column next to the variable. Any time you want to see if you've input enough known values to solve for the others you click on the 'solve' button. If it can find a solution then the calculated values appear in the 'output' column next to the variables that weren't input. And if an iterative solution is needed you can choose which variable to vary, give it an initial value and hit 'solve'.

I can't stress enough how easy it is to use. They must have absolutely DISMAL marketing since this program should sell like hotcakes. I wish someone would buy them out and do justice to it. It could use a little UI updating also, but the foundational concept of its UI is perfect IMO.

[TerraHertz]

Nobody is mentioning Mathematica. Has anyone here tried it?

[MaxSimmonds]

Nobody is mentioning Mathematica. Has anyone here tried it?

I've used it, and as a symbolic solver, it's great. The website offers a very basic version of Mathematica - http://www.wolframalpha.com - helped me a lot when I wanted to check answers to my questions before. It use to (not sure if it does now) show you the process of solving equations to. For example, the breakdown of an integration. IIRC, you were only allowed this 3 times a day, which is one reason the Mathematica package was much much better.

[joeqsmith]

I used to use Borland's Eureka.  Later Mercury.  These are both DOS applications.    I still use MathCAD and believe they still offer it. 

I managed to get a 64-bit version of Octave working.  Pain.   Maybe it's better now. 

[joeqsmith]

Nobody is mentioning Mathematica. Has anyone here tried it?

Now if you want to read an interesting book, look at the history of the guy who wrote it. 

[PartialDischarge]

I’m surprised no one mentioned Derive, extremely powerful and easy to use. Still my prefered for hardcore math. Of course the interface is old, but I started using it with msdos so I’m used to it.

This program can handle algebraic formulas with undefined variables like a juggler. Complex numers? Not a problem. Want to evaluate pi with 20000 decimals? Not a problem. Matrixes? not a problem. Jacobians, gamma functions? Not a problem...

One of the few math programs that can solve ( it does solve it ) an equation like ax^4+bx^3+cx^2+dx+e=0, giving general equations with a,b,c,d,e.

[thermistor-guy]

I’m surprised no one mentioned Derive, extremely powerful and easy to use. Still my prefered for hardcore math. Of course the interface is old, but I started using it with msdos so I’m used to it.

This program can handle algebraic formulas with undefined variables like a juggler. Complex numers? Not a problem. Want to evaluate pi with 20000 decimals? Not a problem. Matrixes? not a problem. Jacobians, gamma functions? Not a problem...

One of the few math programs that can solve ( it does solve it ) an equation like ax^4+bx^3+cx^2+dx+e=0, giving general equations with a,b,c,d,e.

For symbolic manipulation and arbitary precision arithmetic,  I used to use MuPad and MuPad Light:
https://en.wikipedia.org/wiki/MuPAD

Very powerful, like Derive.

[thermistor-guy]

The advantage was you could specify some of the input and output values, and it would solve for the unknowns. In other words, it was up to you which variables were inputs and which were outputs, and you could easily reclassify them.

...
I can't stress enough how easy it is to use. They must have absolutely DISMAL marketing since this program should sell like hotcakes. I wish someone would buy them out and do justice to it. It could use a little UI updating also, but the foundational concept of its UI is perfect IMO.

It was easy to use, and the marketing even back then was dismal. I remember finding a way to use Tk!Solver to calculate the transient reponse of electrical circuits. It was a very impressive application.

[djacobow]

MathCad used to be nice for making a "live" notebook. It had some symbolic solving capabilities, but was mostly a numerical thing.

It looks like it still exists: https://www.ptc.com/en/products/mathcad

[ChunkyPastaSauce]

Sage is pretty awesome, it's worth checking out.

https://en.wikipedia.org/wiki/SageMath
https://github.com/sagemath/sage-windows/releases

[thermistor-guy]

Maxima (computer algebra system) on-line:

http://maxima-online.org/
http://elearning.cerfacs.fr/miscellaneous/tools/maxima/index.php

The OP can try this before downloading anything.

[sibeen]

MathCad used to be nice for making a "live" notebook. It had some symbolic solving capabilities, but was mostly a numerical thing.

It looks like it still exists: https://www.ptc.com/en/products/mathcad

Mathcad went from the standard mathcad to mathcad prime, where the parent company completely screwed the pooch.

I still use mathcad 14 on a daily basis and wouldn't touch the new program with a barge pole.

[djacobow]

Mathcad went from the standard mathcad to mathcad prime, where the parent company completely screwed the pooch.

I still use mathcad 14 on a daily basis and wouldn't touch the new program with a barge pole.

That's a shame. It was a cool piece of software. I used it when it was brand new in the early 1990s. In fact, I think I may vaguely remember a pre-windows version.

[rstofer]

Maxima (computer algebra system) on-line:

http://maxima-online.org/
http://elearning.cerfacs.fr/miscellaneous/tools/maxima/index.php

The OP can try this before downloading anything.

wxMaxima for Windows is excellent.  I use it in addition to Matlab, mostly because I started using it earlier.  I am transitioning to Matlab but if I didn't want to pay for Matlab, Octave and wxMaxima would be my choices.

There are situations where I prefer Fortran...