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Homework Help: Limit of e^(-2x) * cosx as x-> ∞

  1. Apr 18, 2010 #1
    Problem statement: Find the limit of e^(-2x) * cosx as x-> ∞

    Attempt at solution: I tried to say that the limit of e^(-2x) as x-> ∞ is 0, and the limit of cosx doesn't exist since it oscillates between -1 and 1 therefore the overall answer is that it doesn't exist. I was wrong however and the right answer was 0. Could someone please help?
  2. jcsd
  3. Apr 18, 2010 #2


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    Homework Helper

    limit of cos(x) doesn't exist but can you put bounds on its absolute value?

    whats the limit of e^(-2x) times the upper bound?
  4. Apr 18, 2010 #3

    D H

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    Staff Emeritus
    Science Advisor

    Try applying the squeeze theorem.
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