Quick Graph is the best graphic calculator available on the AppStore!

It is a powerful, high quality, graphic calculator that takes full advantage of the multitouch display and the powerful graphic capabilities of the iPad and iPhone, both in 2D and 3D. A simple, yet intuitive interface that makes it easy to enter and/or edit equations and visualize them in mathematical notation.
It's capable of displaying explicit and implicit (opt) equations as well as inequalities (opt) in both 2D and 3D, in all standard coordinate systems: cartesian, polar, spherical and cylindrical, all with amazing speed and beautiful results, which can be copied, emailed or saved to the photo library.

"It's ok to write yet another graphing app, so long as it is the best one. And this is"
-- Review by RightyC1

Please keep in mind that in this version, you now have to specify y=, x=, z= and so on, whenever you want to plot an equation.

The advanced feature set gives you access to some of the new features, such as implicit graphs and tracing. You need to specify the dependent variable now, since just typing "x^2" without the y=, will assume the expression to be "x^2=0" and will try to plot it as an implicit graph.

Up to 6 equations can be visualized simultaneously, in both 2D and 3D modes, this limitation can be removed by purchasing the advanced feature set. All the features from the original application are present and will remain free.

It also includes an evaluate feature, to evaluate equations at specific points, as well as a library where you can store commonly used equations.

Features:
- VGA Output (available with the advanced features package. iPhone 4, 4th gen iPod, and iPad only)
- 2D - 3D equation plotting.
- Library for commonly used equations.
- Wireframe and solid visualization.
- Support for cartesian, polar, cylindrical and spherical coordinate systems.
- Pinch to zoom.
- Drag to rotate - move.
- Swipe to delete equations from the equation list.
- Shake to reset view to original state, or to clear entry fields.
- Double tap to change visualization modes.
- Enhanced 2D mode for great hi-res graphics.
- Adaptive 2D algorithms.
- Enhanced 3D mode with better graphics.
- In-app email so you can share graphics and equations.
- Save to photo library.
- Copy to clipboard.
- Enhanced equation visualization.
- Hyperbolic and Inverse functions.
- New functions such as Min, Max, if.
- Interactive expression evaluation.
- Optionally you can unlock implicit graphs, inequalities and other advanced features (via in-app purchase).
- Turn graphs on/off

The optional advanced feature set includes:
- VGA Out
- 2D tracing.
- 2D and 3D implicit graphs.
- 2D and 3D inequalities.
- Independent 2D zoom
- Roots and Intersections (2D)
- Value Table
- More features to come!

Please visit the website for more details.