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Extending the definition of the summation convention

  1. Oct 4, 2013 #1


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    1. The problem statement, all variables and given/known data

    let a[itex]_{i}[/itex]=x[itex]^{i}[/itex] and b[itex]_{i}[/itex]=1[itex]\div[/itex] i ! and c[itex]_{i}[/itex]=(-1)[itex]^{i}[/itex] and suppose that i takes all interger values from 0 to ∞. calculate a[itex]_{i}[/itex]b[itex]_{i}[/itex] and calculate a[itex]_{i}[/itex]c[itex]_{i}[/itex]

    2. Relevant equations
    i know that in suffix notation a[itex]_{i}[/itex]b[itex]_{i}[/itex] is the same as the dot product as when you have to of the same subscripts you take the sum of a[itex]_{i}[/itex]b[itex]_{i}[/itex] from i=1 to i=3 but i am not really sure
    of how to use the part where it says take interger values of i from 0 to ∞ an explanation would be great .
  2. jcsd
  3. Oct 4, 2013 #2


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    hi ppy! :smile:
    it's asking you for ∑ xi/i! and ∑ (-1)ixi :wink:
  4. Oct 4, 2013 #3
    you actually run i from 1 to ##\infty## not 1 to 3
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