WolframAlpha (http://www.wolframalpha.com/)
is a fun website to just play around with.
They bill themselves as a computational knowledge engine which means I
guess that they’re kind of like an encyclopedia on steroids. If you type in parabola, for example, you
get a nice basic disquisition about a generic parabola. If you type in y=x^2 +4 you get information
about that specific parabola (including its graph, derivative, and global
minimum). If you type in two equations
it’ll give you information about the system (including the graphs &
solutions). All in all it’s just plain
fun to fool around with.
If you haven't used it before & want to see what it's about your best bet is to just click on the examples link and browse around for a bit in your preferred subject areas of interest.
