Summation from a to b

[Guest]

How do you have Excel complete a summation - like what's done in calculus?
For example, I want to know the sum of an equation with variable x, varying x
from constant a to constant b.

 

[Jerry W. Lewis]

Excel is not a calculus engine. That said, you can often create array
formulas that will do simple summations. What did you have in mind?

Jerry

 

[Guest]

Hi,

In Cell A1 enter the constant a. In A2 enter the formula, =A1+0.01*(b-a)
[where b and a are the actual values of those constants]. Now autofill the
formula down column A till A101 [The value in A101 should correspond to b].

In B1, enter the equation as =f(A1) where 'f' is the your function [e.g., if
the function is 3*x^2-2*x+5, the formula in B1 would be =3*(A1)^2-2*A1+5.
Autofill the formula in B1 down to B101.

In C1 enter 0. In C2, enter the formula =C1+(B1+B2)*(A2-A1)/2 [This
formula corresponds to Numerial Integration by the Trapezoidal Rule].
Autofill the formula in C2 down to C101. The value in C101 corresponds to
the integration (summation) of the function with x varying from a to b.

Regards,
B. R. Ramachandran

 

[Bernard Liengme]

See AreaUnderCurve at www.stfx.ca/people/bliengme/ExcelTips