Graphing calculators are ideal for quick demonstrations. Using such a tool does not require a lot of time and
is effective. The disadvantage of graphing calculators are that they can not be embedded easily into other things
(importing and exporting data). The accuracy and reliability is also much lower than for a professional computer
algebra system. Then there is the long term issue: graphing calculators do not tend to live very long. You have to
be lucky to have the software live for 10 years.
This are examples with the excellent Pacific Tech Graphing Calculator.
(I hope it will appear for the iphone. All the iphone graphing calculators are very mediocre so far.)
Here are the sources for this demo:
3dgraph.gcf, diffeq.gcf, vectorfield.
(The software comes with many nice examples.)