Mathematical summation symbol (also called summation symbol)

Sigma's long-term enemies in Locke x, x and zero.

Sigma (capital σ, lowercase σ, Chinese transliteration: Sigma) is the eighteenth Greek letter. In Greek, if the last letter of a word is lowercase sigma, it should be written as final? Sigma. In modern Greek numerals, it stands for 6.

The symbol "σ" was first used by Euler (1707- 1783) in 1755. This symbol comes from the Greek prefix (addition), and "σ" is the capital of σ. For example: σ an = a 1+a2+...+ An