Writing an Integral Midpoint,Trapezoidal,Simpson Rule

I need Help in writing an expression in excel for the attached question:
a) Midpoint Rule
b) Trapezoidal Rule
c) Simpson

I have found one document that solves the simpson method and modified it to work with my given equation but not sure if its right or not(Check the Simpson-modified excel file attached)




Integral.pdf
Simpson-Modified.xls

At first glance, without looking at it in great detail, Professor Lira's spreadsheet looks correct. My main concern is, since this looks a lot like a homework assignment, is whether or not using a spreadsheet harvested from the internet will really fulfill the requirements of the assignment.

I would probably use a similar spreadsheet layout for the midpoint and trapezoidal rules (and left and right hand sums if those were part of the assignment). If you can be specific about the questions you have, we should be able to help you learn how to do definite integrals numerically in Excel.

given to us without having any knowledge in handling definite integrals in Excel

I firmly believe that it is important, before trying to program something like this into a spreadsheet (or any other programming language), to understand the math behind it. Even if you are unfamiliar with using Excel for numerical integration, can I assume that you have had calculus and understand, at least in generic terms, how these Riemann sums work? If needed, I might suggest that your first be to review a calculus text and/or any internet tutorials you can find for these Riemann sums (Wikipedia has a decent page).

Once you understand the basic algorithm, programming it into a spreadsheet is about programming those same steps into spreadsheet cells. As I noted above, I would probably use a similar layout to Professor Lira's spreadsheet. Calculate f(xi) for each point/subdivision and each method of the definite integral in one row. Copy that row down until all subdivisions are calculated. Then use a =SUM() function to add up the area of each subdivision to get the approximation of the definite integral.