Live data from Hacker News

A First Course in Differential Equations for Scientists and Engineers

people.uncw.edu

51–60 of 67 posts

Re: A First Course in Differential Equations for Scientists and Engineers

#51

On a related note, how do you take notes for math subjects with their multiline integrals and sumation and subscripts, division etc? I'm very much attached to recording every thing in simple text editors. Is there a "Notepad" or "TextEdit" for mathematical notation?

I've been playing around with: http://asciimath.org/

Re: A First Course in Differential Equations for Scientists and Engineers

#52
post #49

While the linked course seems a lot more thorough, I took the Udacity "Differential Equations in Action" [1] course, which I found very well done. For the homework you write Python programs to compute things like gravitational slingshots, modeling epidemics, wildfires, and the n-body problem. [1] https://www.udacity.com/course/differential-equations-in-act...

I took the first part of that course, enough to write an n-body game: https://github.com/madengr/nbody While it was a good course, I wish it covered the analytic portion, rather than dive straight into numerical solutions.

That is pretty neat. Improvements on the analytic side (if you are interested in the opinion of a random person on the internet) would be to scale your coordinate system (e.g. scale the distance and time to make average velocity and radius equal 1) and look into using a symplectic integrator. Better for these types of systems.

Re: A First Course in Differential Equations for Scientists and Engineers

#53
The usage of terms 'initial value' and 'boundary value' is a massive failure of mathematics education.

'Initial' refers to time-like variables, and 'boundary' refers to space-like variables.

There is no notion of time in mathematics. There is only a notion of space, due to geometry. I had the longest time coming to grips with the question, "mathematically what is the difference between initial value and boundary value?" only to realize the distinction is meaningless in mathematics. It's a relic of the past when differential equations were studied under physics, where time and space are a huge part of the conceptual foundation.

Sometimes I wonder how much progress we would make in education if we didn't confuse the heck of our students in the name of convention and historical baggage.

Re: A First Course in Differential Equations for Scientists and Engineers

#54
post #4

Lately I have been looking for a practical (not too much theory) book on how to model problems with differential equations, with lots of examples. I imagine I'd plug them into Wolfram Alpha to get a solution. Does anyone have recommendations?

You can also look into "system dynamics" software, which allows for the modeling of complex systems with very little user-facing mathematics. Dana Meadows wrote a book called "Thinking in Systems," which is a great intro to this subject.¹ I personally have used Stella by isee systems, which will output an equation from your model if you are so inclined, but I think there is cheaper/free software out there that will d…

Thanks, that looks very interesting!

Re: A First Course in Differential Equations for Scientists and Engineers

#55
post #53

The usage of terms 'initial value' and 'boundary value' is a massive failure of mathematics education. 'Initial' refers to time-like variables, and 'boundary' refers to space-like variables. There is no notion of time in mathematics. There is only a notion of space, due to geometry. I had the longest time coming to grips with the question, "mathematically what is the difference between initial value and boundary valu…

Since time is 1D while space may have more dimensions, initial values are connected to ODEs while boundary ones with PDEs. Their behavior is quite different.

Re: A First Course in Differential Equations for Scientists and Engineers

#56
post #7

Look at Arnold's book on Diff, it is harder then others, but has absolutely different outlook.

I can only find the first edition on Amazon, but there's apparently a third edition? http://www.matem.unam.mx/ernesto/EDO/Ar-EDO.pdf

https://www.amazon.com/Ordinary-Differential-Equations-MIT-P...

Re: A First Course in Differential Equations for Scientists and Engineers

#57
post #49

Earlier quoted context omitted.

I took the first part of that course, enough to write an n-body game: https://github.com/madengr/nbody While it was a good course, I wish it covered the analytic portion, rather than dive straight into numerical solutions.

That is pretty neat. Improvements on the analytic side (if you are interested in the opinion of a random person on the internet) would be to scale your coordinate system (e.g. scale the distance and time to make average velocity and radius equal 1) and look into using a symplectic integrator. Better for these types of systems.

Thanks. I remember in the course, keeping the energy constant is the big issue. They used the symplectic integrator to improve it. In the game, if you let it run long enough, the error visibly shows up.

Re: A First Course in Differential Equations for Scientists and Engineers

#58
post #56
post #7

Look at Arnold's book on Diff, it is harder then others, but has absolutely different outlook.

I can only find the first edition on Amazon, but there's apparently a third edition? http://www.matem.unam.mx/ernesto/EDO/Ar-EDO.pdf https://www.amazon.com/Ordinary-Differential-Equations-MIT-P...

I think this is the third edition: https://www.amazon.com/x/dp/3540345639

Re: A First Course in Differential Equations for Scientists and Engineers

#59

On a related note, how do you take notes for math subjects with their multiline integrals and sumation and subscripts, division etc? I'm very much attached to recording every thing in simple text editors. Is there a "Notepad" or "TextEdit" for mathematical notation?

There's TeXmacs, which lets you enter mathematics either via point-and-click palettes or using TeX notation. I like it a lot. Downsides: 1. Development seems more or less dead. 2. It's not always been perfectly stable. 3. It's kinda sluggish, especially on older slower machines.

Re: A First Course in Differential Equations for Scientists and Engineers

#60

Earlier quoted context omitted.

> I really don't think that such topics can be self-studied Can you explain this? What makes something extremely difficult to be studied without a teacher? (I took calc in high school and never took diff eq, so my knowledge in this specific domain is basically zero)

Diff. eq. is a difficult topic. Not only you need to have a good understanding of a lot of other mathematic topics (derivatives, integrals etc) to properly understand it since it builds upon those but you also need somebody to guide you on how to think when solving such problems (i.e you'll need to solve diff. eq. together with your teacher).

Yeah - I never studied differential equations in college; I sort of know what they are, and that there's a famous problem that involves a snow-plow plowing a field while it's still snowing, but that's about it. I've always been curious, though, so I clicked through the link. Per the introduction, I jumped ahead to the "what do you need to know from calculus" appendix just to see how much I did remember. Derivatives, integrals, ok, sure I remember that. Trigonometric functions? Um, yeah, I think I remember that - adjacent over hypotenuse, tangent, theta, sounds familiar. Half-angle, double-angle... getting rustier, but I think I remember that stuff. Hyperbolic functions? Oh, boy... yeah, something to do with the way power lines hang. I remember remembering that once. Integration by parts? Oh, man, I don't know if I ever learned that. Geometric series? Power series? Binomial expansion? I read about those in TAOCP, but if I ever studied those in class, it went in one ear and out the other. And that's what I need to know to start reading... maybe I do need a teacher.
Post reply on HN