SecantTangent Applet
The SecantTangent applet is a special purpose applet that shows secant lines converging on a tangent line. The applet
draws a tangent line to a graph at a point marked by a draggable disk
(red). By dragging this disk, you can move
the point. A secant line is drawn from this point to another point,
which is marked by another draggable disk (green).
You can also set the x-coordinates of the points by entering them in
the input boxes at the bottom of the applet. The slopes of the two lines
are shown at the upper left, but you can turn off the display of the tangent
slope if, for example, you want the user to estimate the slope of the tangent
line from the slopes of secant lines.
The applet below provides a gallery of examples in the drop-down menu at the top. Also, mouse actions are turned on (click, shift-click, click-and-drag, and right-click-and-drag).