This app can be used to find the slopes of secants to the curve of [math]f(x)=\frac{1}{x}[/math] (in blue). Sliders are provided to move either [math]x_1[/math] or [math]x_2[/math]. The calculation of the slope is shown. By moving [math]x_2[/math] very close to [math]x_1[/math], this app can be used to find an approximation for the slope of a tangent to this curve. Alternatively, you can type "x_2=" followed by your choice of the [math]x_2[/math] value in the input bar at the bottom.

The function [math]f(x)[/math] can be changed by typing another function into the input bar.