# Sum and Product Notation

The sum notation uses the capital Greek letter sigma as follows:

Thus if x1 = 6, x2 = 7 and x3 = -2, then

Note that index i can be replaced by any other index and the results will be the same. Thus,

Also the initial value doesn’t have to be 1. For example, assuming k ≤ n

The initial value can also be –$\infty$ and/or the final value can be +$\infty$.

We can iterate the use of the sigma notation. For example,

We can also use abbreviated notations such as the following:

There is a similar notation for products using the capital Greek letter pi:

### 2 Responses to Sum and Product Notation

1. Grace says:

Hi,
Is it possible to do the Capital Pi (Product) function on Excel?

Here is what I need to do, using an example with the first three rows (it will go up to 101 rows):

1st row Y_1=x_1 (1-z_1)
2nd row Y_2=x_2 (1-z_1)(1-z_2)
3rd row Y_3=x_3 (1-z_1)(1-z_2)(1-z_3)

Any advice would be greatly appreciated. Thank you!

• Charles says:

Grace,
There is a product function in Excel that you could use. If R1 is a range then =PRODUCT(R1) returns the value which is the product of the values of all the cells in R1.
Charles