∑ English name: Sigma (capital σ, lowercase σ), with18th Greek letter. In Greek, if the last letter of a word is lowercase sigma, what should it be written as? This letter is also called final sigma(Unicode: U+03C2). In modern Greece, this number stands for 6. Management method, one sigma is equal to one in a million. In production, six sigma (3.4 parts per million in mathematical calculation and 6 parts per million in management) is used to represent the normal defects that millions of products can have.

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abstract

Capital σ is used for mathematical summation symbols, such as ∑Pi, where i= 1, 2, ..., t, which is the sum of P 1+P2+ and ...+angle. Lowercase σ is used for statistical standard deviation. Both the с of Cyrillic alphabet and the S of Latin alphabet are derived from Sigma. It also means summation, which means ∑ j =1+2+3+…+n.

Detailed comments

1, the ∑ symbol means sum, and ∑ is pronounced as sigma, which means sum in English and is the sum. The method of expressing sum with ∑ is called ∑ symbol. Its lowercase is σ, which is often used in physics to represent the area density. (Accordingly, ρ stands for bulk density and η stands for linear density) 2. Usage of ∑: n ∑ k i stands for the lower bound, n stands for the upper bound, and k from I to n is all added up. I ∑ i can also be expressed as the sum of I, where I is a variable such as100 ∑ I =1+2+3+4+5+...+100I =1200 ∑ I = 5+6+. = 10+ 1 1+ 12+ 13+ 14+......+500 i= 10 444 ∑ Xi = X？ + X？ + X？ + X？ +......+ X？ I = 1.50 ∑ I = 1+2+3+4+...+50 = 1275 I = 1.70∑x = x+x+...+x = 70x 1。 Recursion 50 50 ∑ (n+1) = ∑ n+∑1= 20+21+...+50+31×1/kloc-.