We are going to see how right-hand rectangles approximate the area under the curve. A right-hand rectangle means that the height of the rectangle is determined by where the right endpoint lies on the function.
The slider a determines the number of rectangles.
Why does it say that there is currently one rectangle but none are visible?
Drag the slider to increase the number of rectangles. What happens as the number of rectangles increases?
Under what conditions would a right-hand approximation always be too big? Too small?