Exploring Upper and Lower Riemann Sums

Author:
DNghiem
The Upper Sum S(n) is shaded in Blue. The Lower Sum s(n) is shaded in Brown.
Question: How are the heights of each rectangle found for the Upper Sum ? Question 2: How are the heights of each rectangle found for the Lower Sum? Question 3: Give a convincing explanation about why the area of the region bounded by f(x) and the x-axis between x = 1 and x= 3.2 is between 4.53 and 4.76