How is Sigma Used in Mathematics?

[DB]

wondering how "sigma" is used

I think this is the right forum. I wondering how "sigma" is used, the definition is summation but what does that mean, is it just the sum? Can some 1 give me an example of how it works. Thnx.

 

[daster]

\sum^{n}_{i=0} f(i)

This is the sum of f(i) from i=0 to i=n, i.e.

f(0) + f(1) + f(2) + ... f(n)

 

[Galileo]

If you are referring to sigma notation (with the Greek letter \Sigma). It's a convenient way of writing sums.
Suppose you have a sequence of numbers a_m,a_{m+1},...,a_n and you want to add them, then:

\sum_{i=m}^na_i=a_m+a_{m+1}+...+a_n

The i is a variable used for counting. The i=m at the bottom tells us to start with i=m and the n at the top tells us to end with i=n.

For example:
\sum_{i=1}^7 i= 1+2+3+4+5+6+7

\sum_{i=5}^9 i^2= 5^2+6^2+7^2+8^2+9^2

\sum_{j=0}^5 2^j=2^0+2^1+2^2+2^3+2^4+2^5

etc.

 

[DB]

lol i kinda see it but its a bit unclear to me, maybe a simpler example lol thnx

 

[DB]

lol thnx galileo i see it