
Doug C. answered 01/23/21
Math Tutor with Reputation to make difficult concepts understandable
If you divide the interval from 1 to 2 into 5 equal subintervals. each subinterval has a width of .2: (2-1)/5.
The left hand endpoint of the 1st subinterval will be 1 and the right hand endpoint 1.2. The midpoint of that sub interval will be 1.1: (1 + 1.2)/2.
Using that midpoint to calculate the height of the 1st rectangle is found as f(1.1) = .909.
The area of the 1st rectangle is given by f(1.1) (.2) [height time width], which is .1818.
Proceed in a similar fashion for the remaining four rectangles, adding the areas to get approximation for the total area.