AP Calculus Unit 2.1 Rates of Change - general

Construction similar to one used in AP Daily video Unit 2.1 (2020-21 academic year), intended to show how:
  1. "average rate of change" may be interpreted as the slope of a secant line over an interval
  2. "instantaneous rate of change" (a.k.a. derivative) may be interpreted as the slope of a tangent line at a single input value
  3. instantaneous rate of change is the limit of the average rate of change as the width of the interval shrinks to zero.
To change the interval width, drag either of the edges left/right. To change the location of the tangent line, drag the blue point of tangency within the interval. Click/drag on an empty part of the grid to pan left/right/up/down. Use a scroll wheel to zoom in/out. Shift-Click/drag on an axis to change its scale. Original version of this construction is here, with function used in the AP Daily Unit 2.1 video.