Simpsons rule in excel

Charlie2013

I have a computers assignment and have to use simpsons rule in microsoft excel to get the answer.

a = 0
b = 20

Sin (pi x/100)

n = 20

I dont even know where to start! Any help if very much appreciated. Thanks

Bit cynical

Going on the information on this page:
http://www.intmath.com/integration/6-simpsons-rule.php

Down a bit the page shows a memory aid:

(delta x/3)(FIRST + 4(sum of ODDs) + 2(sum of EVENS) + LAST)

This is not a very elegant way but should work. You need to be able to enter a formula that refers to other values by pointing the cursor.

Create columns headed FIRST, ODDs, EVENs, LAST with empty columns in between them. FIRST will just hold the single number zero and LAST will contain the single number 20. So the FIRST column will look like:

FIRST
0

and the LAST column will look like
LAST
0

Below the ODDs, put all the odd numbers between 0 and 20 exclusive: (1, 3,..., 19). Excel has a quick way of doing this: you put in 1 and then 3 below it. Highlight both cells and then drag the corner down. It will generate the numbers.

Below the EVENs, likewise put all the even numbers between 0 and 20 exclusive: (2,4,...,18).

You now have four columns with spaces between.

Under the FIRST column you have zero. To the right hand side of this zero put the formula =SIN(PI()*x/100) but instead of x have it refer to the the zero immediately to the left. It should evaluate to zero when you have entered it.

Now copy the cell containing the formula to all the values of the other columns so that for each value of x you have a value for the function.

You should now have values of the function for FIRST, the ODDS, the EVENs and the LAST.

You now need to sum up the values in each of these columns. The important sums are (sum of ODDs) and (sum of EVENSs)

Now put in somewhere below as a formula:

= (FIRST + 4*ODDs - 2*EVENs + LAST) / 3.

Note that you don't type in FIRST, ODDs, EVENs and LAST. These refer to already calculated sums. You need to point to these when entering the formula.

This should give you your integral.

Note that we've left out the interval delta x. This is because delta x is (b - a) / n = (20 - 0)/20 = 1. This should be easy to calculate in excel.

prosaic

OP, do you get the idea behind Simpson's rule?
Perhaps your assignment is done and dusted by now, but thought I might ask anyway.

Charlie2013

prosaic wrote: »

OP, do you get the idea behind Simpson's rule?
Perhaps your assignment is done and dusted by now, but thought I might ask anyway.

Not really. I got one of the lads to send me their one and i just made it my own. I passed anyway