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Help me find a limit!

  1. Sep 20, 2010 #1
    1. The problem statement, all variables and given/known data
    Find the limit of e(-t/2)((k/2)t+c) as t approaches infinity where k and c are constants


    2. Relevant equations
    Not sure..?


    3. The attempt at a solution
    Plugging in t = infinity gives me an indeterminate form, and multiple applications of L'hopital's rule have led me no where. Any suggestions? I can see graphically that it goes to 0, but I'm not sure how to show this analytically. I can see that if I expand it, the e(-t/2)c term goes to zero, but I'm not sure about the other term.
     
  2. jcsd
  3. Sep 20, 2010 #2

    rock.freak667

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    I do not know if this is a valid form of proving limits, but e-t/2 approaches 0 faster than any polynomial can approach infinity as t→∞.
     
  4. Sep 20, 2010 #3
    yeah I was hoping that L'hopital's rule would show that but it didn't work out...
     
  5. Sep 20, 2010 #4

    rock.freak667

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    Wouldn't L'Hopital's rule as show it going to zero since d/dt{0.5kt+c} is does not contain a tern in 't'?
     
  6. Sep 20, 2010 #5
    Oops! yes! Thank you, I found my mistake.
     
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