I could not imagine trying to take notes with a computer in a math heavy subject. I had to use paper for everything during my undergrad in Civil Engineering. However, if you already have a computer with you, record the lecture and review it later.

Just as a partial counterpoint to this and overall agreement with everyone else who responded, I've had success taking realtime notes on my laptop in a math class. It took a bit of practice and I'm sure I can't do it anymore, but it's not insurmountable by any means.

I used latex and made liberal use of keyboard and software macros to do it, and one of the tricks was to realize that if I needed a quick-to-type way to typeset new thing X, I should just pretend I had such an implementation and make up its command on the spot. At my leisure, I could write up a conforming latex command that worked with all the notes I'd taken in realtime.

That said, I've since come to realize that math notes don't help me as much as they seem to help others. I have greater success primarily listening during class and leaning on the textbook as well as online resources outside of class. I do second the use of emacs to handle the latex, but I don't think that realtime rendering is particularly important in a notes setting.

Excellent counterpoint. Keep in mind that I was a Civil Engineering student, not computer science. My abilities to use Latex were little-to-none at the time. I didn't get any exposure to it until I was in grad school and we used it to format journal article submissions.

Don’t. Pay attention, write down the things that aren’t in the text book. And then learn to read the text book. It’s a hugely valuable skill.

I'm easily distracted, particularly from internal digressions. Taking notes helps me hold on to the thread.

Do not deprive yourself of the delight of browsing through your handwritten notes some years in the future!

I use mathstackexchange for that purpose and do all my work in the little window where they want you to type up your question. I don't ask/answer questions on there. Mathjax will render all your stuff beautifully. If I want to save my work, I just take a screenshot.

This link below is a great reference that's worth keeping around:

https://math.meta.stackexchange.com/questions/5020/mathjax-b...

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.

Not exactly what you're looking for but a near fit: http://www.wolframalpha.com/input/?i=derivative+of+x%5E4+sin...

you can use LaTeX notation and then render it with something.

For example MathJax, or emacs's org-preview-latex-toggle to show the rendered equations in the same buffer you write in.

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