This is a terminal calculator with a remarkable twist.
It uses symbolic differentiation to provide a numerically
precise error estimate with each calculated answer.
It mimics the functionality of an HewlettPackard Reverse Polish Notation [RPN] calculator simply because I like RPN. But along with your answer, you get some measure of its trustworthiness. Runs on PCs or laptops running Windows or Linux.
The output of this calculator has been tested against my interval calculator, that uses interval arithmetic, which is very much more complex. The results and error estimates are completely consistent. Reference: