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Re-writing a PDE

  1. Nov 13, 2014 #1


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    1. The problem statement, all variables and given/known data
    Provide the missing steps to re-write the equation into one with just two terms $$u_{tt} - c^2(u_{rr}+\frac{2}{r}u_r) = 0$$

    2. Relevant equations
    Nothing, other than this looks similar to the wave equation hybrid. (I'm just speculating)
    Also, I'm a little uncertain what is being asked.

    3. The attempt at a solution
    Well nothing comes to mind. I am looking at this term: ##u_{rr}+{2}u_r/{r}##. So far nothing huge is coming to mind. I initially tried something like ##(u_r/r)'## and then ##(u_r \ln r)'## since they looked close to the above but nothing helps. Any creative ideas out there?

    Thanks a ton
  2. jcsd
  3. Nov 13, 2014 #2


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    Try multiplying both sides by ##r^2##.
  4. Nov 13, 2014 #3


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    Brilliant! Thanks a ton!
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