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Logarithmic identity help?

  1. Aug 23, 2011 #1
    This is related to differential equations, but I think my question has more to do with log identities than DE.

    I keep seeing equations like

    1/8 lny = t + c

    simplified to get the solution

    y = ce^8t

    but I am unsure of the identity being used to get 1/8 into the exponent as 8. I already understand how everything else is simplified, just not this part. Thanks!
  2. jcsd
  3. Aug 23, 2011 #2


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    Just multiply both sides by 8 and exponentiate both sides.

    The other way to see this would be that [itex]1/8 ln(y) = ln(y^{{1}\over{8}})[/itex]
  4. Aug 23, 2011 #3
    *facepalm* Thanks penguwino LOL
  5. Aug 23, 2011 #4


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    Gold Member

    That'll be $5
  6. Aug 23, 2011 #5
    I'll give you $25 :tongue2:

    I kept switching it over the entire semester and never understood why I was doing that loll. This is what happens when the "simple steps" are skipped in math -_-
  7. Aug 23, 2011 #6


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    Gold Member

    Tattoo the logarithmic identities to your forearm. It's far more useful then some rose or star
  8. Aug 23, 2011 #7
    ^ But then to avoid being suspected of cheating, you'd have to wear full-sleeve shirts during your exams. And that sucks when your exams are seated outside during a heatwave :(
  9. Aug 23, 2011 #8
    I'll see if I can have them burned on my retina :D
    That is so sadistic! -_- Who would ever do such a thing to an innocent student?
  10. Aug 23, 2011 #9

    I like Serena

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    Homework Helper

    Try to burn them behind your retinas.
    That works even better! ;)

    Oh, standard trick to flush out not-so-innocent students.
  11. Aug 23, 2011 #10
    If there was something behind my retinae it would work better :tongue2:
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