Combining multiple devices into one has always been a boon of smartphones like the HTC EVO. It's already a camera, eReader, telephone, to do list, and so many other things, and now it is a homework tool too. ECCalc Pro allows you to perform those oh so tricky trigonometry and graphing problems that your teacher assigned you with ease.
ECCalc Pro is the brains of what is essentially a two-part app. It allows for calculations involving items such as pi, natural log, and exponential equations, and also has the ability to graph equations. The second part is ECCalc Keyboard, which lets you easily enter all these odd characters with ease. ECCalc Pro is useable without the keyboard component, but the latter certainly makes it more robust and flexible.
Currently both apps are listed as free through AppBrain.
[ECCalc Pro | ECCalc Keyboard]