I stands for the lower bound, n stands for the upper bound, and k starts from I and goes all the way to n, all of which add up.

Examples are as follows:

∑(i= 1, n = 5) k =1+2+3+4+5 =15. The lower bound I is written below the lower horizontal line, the upper bound is written above the upper horizontal line, and k is written in the middle of the two horizontal lines. The specific writing is as follows:

∑ (summation symbol)

English name: Shima

Chinese name: Sigma (capital σ, lowercase σ)

The eighteenth 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.

Extended data:

Other summation formulas:

1。 ? 1+2+3+......+n=n(n+ 1)/2

2。 1^2+2^2+3^2+......+n^2=n(n+ 1)(2n+ 1)/6

3。 1^3+2^3+3^3+......+n^3=( 1+2+3......+n)^2=n^2*(n+ 1)^2/4

4。 1*2+2*3+3*4+......+n(n+ 1)= n(n+ 1)(n+2)/3