This tool estimates $f'(x_0)$ using a difference quotient. Enter a simple expression in x, a point $x_0$, and a step size $h$. Central differences are usually best for smooth functions; try smaller $h$ until the estimate stabilizes — then stop before floating-point noise dominates.
Allowed pieces: numbers, x, + - * / ^, parentheses, and sin cos tan sqrt abs log (natural) exp pi e.