I had a dream, way back, perhaps a decade ago, before there were anything remotely looking like ipads: "One day learning will be evolved by interactive books"
My original vision was PDF files can be embedded with little programs, like there are some movable elements in children's books.
I accumulated a decade of programming into this app: Math Experiments.
These are originally written as java applets accompanying my book. http://www.amazon.com/Math-Journey-Joseph-Mak/dp/B004J0T3SW
I converted the helpless applets into Android. Applets are now warned with yellow bars or won't run at all. Applets are so 1990s. However, android view programming has a lot of same ideas as applets... and android can do more, even OpenGL 3D graphics (which my little math experiments do not require).
So now you can enter your own parameters and experiment with it. How I so much want a calculator to do fractions for me when I was doing drills in elementary school. I long hoped to play interactively with the parameters that move the sine wave (like the knobs on the oscilloscope) and parabola.
The limit as h->0 can now be shown visually out of imagination. yippee.
Get yours free
at the Android Market