Deriv

Deriv is easy to use and very fast because it uses its own built-in engine for differentiating functions and hence doesn't rely on slow third-party services. The most notable features of this app are:

- Evaluation: after computing a derivative, you can quickly evaluate it by providing values for variables. It's very easy and convenient.

- Persistence: everything you do is stored in a database on your device, this way you can easily recover all your previous computations when you need them again.

- Beauty & Clarity: all mathematical expressions are rendered with KaTeX and look just awesome. Also, Deriv's differentiation engine tries its best to make the resulting functions as clear and readable as possible.