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Wondering how sigma is used

  1. Dec 22, 2004 #1


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    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.
  2. jcsd
  3. Dec 22, 2004 #2
    [tex]\sum^{n}_{i=0} f(i)[/tex]

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

    f(0) + f(1) + f(2) + ... f(n)
  4. Dec 22, 2004 #3


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


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

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

    [tex]\sum_{i=5}^9 i^2= 5^2+6^2+7^2+8^2+9^2[/tex]

    [tex]\sum_{j=0}^5 2^j=2^0+2^1+2^2+2^3+2^4+2^5[/tex]

  5. Dec 22, 2004 #4


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    lol i kinda see it but its a bit unclear to me, maybe a simpler example lol thnx
  6. Dec 22, 2004 #5


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    lol thnx galileo i see it
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