What is better to write the lecture on a netbook?

You are on the right track. It is better to understand the elegance and the rigor of the Latex and not to focus on the secondary.
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PS If the teacher after a training session does not give the contents contained in electronic form and if the activity at the University for the most part consists in writing said teacher is a crappy University, consuming valuable younger years.
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Although the above — utopia for most of our educational institutions.

About latehe (it is not latex, by the way) I'm not sure. Know him well enough, but the set of equations it is still somewhat slower than by hand. Besides, if You are not so evil as LaTeX-based WYSIWYG-editors, to compare written on the Board and You have on the laptop will be problematic, especially in the case of cumbersome formulas. And compiling each time and check the time, and if you make some small mistakes, a lot of time (relative to the speed of doing lectures).

still try to write by hand. The method of writing affects the person.

Gaining or in word, or OneNote. Graphs and charts using cellphones/redraw in a notebook, then scan. Those are good, especially on matoha where mathematical formulas a lot. At the same Matane, Matysik there is any, and so in order to make it convenient — it is necessary to write funkciju substitute and simplify the principal terms used... This is hard to do on the fly — especially not look particularly where nakosyachil... in real time in any. But at home or on the break error in a complicated formula may not notice, and then because of this on the exam "to fly". Therefore, the formula at the time was shot on camera. To verify the correctness. Or again — in a notebook.

I write in Microsoft OneNote 2010 — I like it!

try to buy a small entry-level tablet for sketching graphs approach, many software works with the insert drawn with a tablet in 2 clicks

Try The Q10. This is certainly not the LaTeX, but if you are in the lecture will be in writing, to the attention of old professors you provided (turn on sound :) )