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Homework Help: In the limit as A --> ∞, what does the function become?

  1. May 15, 2016 #1
    1. The problem statement, all variables and given/known data
    The function is fA(x) = A, |x| < 1/A, and 0, |x| > 1/A

    2. Relevant equations
    δ(x) = ∞, x=1, and 0 otherwise

    3. The attempt at a solution
    I think the answer is the Dirac delta function, however I noticed that if you integrate fA(x) between -∞ and ∞ you get 2, which if I remember rightly to be a Dirac delta function this should be 1? So perhaps the answer is 2 x δ(x)?
    I'm not sure what's correct, so any help would be greatly appreciated, thank you!
  2. jcsd
  3. May 15, 2016 #2


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    2017 Award

    Staff: Mentor

    2 times the delta distribution (it is not a function), correct.
    Avoid using x as variable and multiplication sign at the same time, please. * is the typical multiplication sign in ascii.
  4. May 15, 2016 #3
    Great thank you, and apologies, I'm aware it's not a function but a measure, but alas my lecturer uses the term function and so it's stuck with me. As for x for multiply, laziness is all, sorry... thanks again, much appreciated :)!
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