Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Dirac delta function

  1. Jul 22, 2011 #1
    1. The problem statement, all variables and given/known data

    attachment.php?attachmentid=37434&stc=1&d=1311345723.jpg

    2. Relevant equations



    3. The attempt at a solution

    Can I write, say, [itex]f(x) \delta(x)=f(2)\delta(x)[/itex]?
    Since [itex]\delta(x)[/itex] =0 for x[itex]\neq[/itex]0
     

    Attached Files:

    • 1.jpg
      1.jpg
      File size:
      95.7 KB
      Views:
      132
  2. jcsd
  3. Jul 22, 2011 #2

    hunt_mat

    User Avatar
    Homework Helper

    I think you can say [itex]f(x)\delta (x-2)=f(2)\delta (x)[/itex]
     
  4. Jul 22, 2011 #3
    Then if x=2, left hand side will become infinity and the right hand side 0.
    Is it Ok?
     
  5. Jul 22, 2011 #4
    So what's wrong with my post in #1?
     
  6. Jul 22, 2011 #5

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    The integral of [itex]f(x) \delta(x)[/itex] over x is f(0). The integral of [itex]f(2) \delta(x)[/itex] over x is f(2). So no, they aren't the same.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook