Algeo is the most beautiful scientific graphing calculator available on the Play Store. It's fast and powerful and you'll never have to carry around a large physical TI calculator anymore. The intuitive interface shows your drawn functions as you would write them on paper rather than squeezing everything on a single line. And you don't need an internet connection unlike other graphing calculators, it works offline as well! Useful for calculus, physics or to solve those x+y equations, graph of qu