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Homework Help: Expectation value problem

  1. Nov 16, 2008 #1
    1. The problem statement, all variables and given/known data

    Calculate [tex]\Delta x = \sqrt{\left\langle(x - \left\langle x \right\rangle )^2 \right\rangle}[/tex] if [tex]\left\langle x \right\rangle = 0 [/tex] and [tex]\left\langle x^2 \right\rangle = a^2(\frac{\pi - 6}{12 \pi^2})[/tex]

    2. The attempt at a solution

    [tex]\left\langle(x - \left\langle x \right\rangle )^2 \right\rangle = \left\langle x^2 - 2x \left\langle x \right\rangle + \left\langle x \right\rangle ^2 \right\rangle[/tex]

    How can I proceed here?

    (Also, can sby tell me the name of the markup language I am using?)
     
    Last edited: Nov 16, 2008
  2. jcsd
  3. Nov 16, 2008 #2

    Dick

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    Take the expectation value of each of those three terms. You are using TeX.
     
  4. Nov 16, 2008 #3

    HallsofIvy

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    You are TOLD that <x>= 0. Put that in and your formula simplifies enormously!
     
  5. Nov 16, 2008 #4
    If I could not simplify, could I write [tex]\left\langle \left\langle x \right\rangle \right\rangle = \left\langle x \right\rangle [/tex]?
     
  6. Nov 16, 2008 #5

    Dick

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    <x> is a constant (i.e. not a function). <constant>=constant. Of course those are equal.
     
  7. Nov 16, 2008 #6
    Lol. Stupid question.
     
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