The Limit of the Secant Line is the Tangent Line
Change the position of the green tangent point using the slider at the top. A tangent line is shown along with the value of its slope, the Instantaneous Rate of Change (IROC). Use the slider at the bottom to move the red point, which forms a secant line with the tangent point. The slope of the secant line is the Average Rate of Change (AROC).
What happens as the two points used for the secant line get closer to one another?
When the secant line disappears? what happens?