Summation from a to b

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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.
 
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
 
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
 
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