Symbols, such as letters, are used in math as shorthand to represent quantities or express processes. One such symbol looks like a capitol E but is actually sigma, the 18th letter of the Greek alphabet. In math, sigma means "sum it up."

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## History

The Swiss mathematician Leonhard Euler, born in 1707, was the first person to use the sigma symbol to represent the addition of a series of math terms. He is the "father" of a number of symbols, or notation, used today in higher mathematics.

## Sigma Notation

In a typical notation summation problem, the math sentence begins with the phrase including sigma topped by the number 4 and with another phrase, "k=1", underneath. "K" equals the beginning term and together with 4 indicates that the phrase equals the sum of (2k + 1) from 1 to 4.

Plug all numbers from 1 to 4 into the general term, (2k + 1) in this case, and then add the terms together.

```
(2(1) + 1) = 3
(2(2) + 1) = 5
(2(3) + 1) = 7
(2(4) + 1) = 9
3 + 5 + 7 + 9 = 24.
```

## Function

Sigma, or summation notation, helps mathematicians identify the numbers in a series that follows a pattern, which may be lengthy, and to add them up. It is a handy way to show where the series begins and ends.