Secant and Tangent Line Slopes
The applet below lets you compare the slope of the secant line between two points (A & B) to the slope of tangent line to point C. The x-coordinate of Point C is the midpoint between the x-coordinates of Points A and B. The slope of the secant line and tangent line are displayed at right. To change point A & B, type a value in the appropriate box at right then press enter. Zoom in or out by right clicking. Use the check boxes to try three different functions.