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Homework Help: Compute lim as x approaches 0

  1. Dec 12, 2009 #1
    1. The problem statement, all variables and given/known data

    http://i45.tinypic.com/20rsnis.jpg

    2. Relevant equations

    Compute the lim

    3. The attempt at a solution
    I tried using l'Hopital's rule but I have to keep finding the derivative and it doesnt yield an answer. I have to use taylor series for the trig functions, but don't know how this will work
     
  2. jcsd
  3. Dec 12, 2009 #2

    Dick

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    Science Advisor
    Homework Helper

    Go ahead, try it. Expand cos(2x) and sin(x) in a taylor series. See which terms cancel. If you don't know the expansion of cos and sin, they are easy to look up.
     
  4. Dec 12, 2009 #3
    http://en.wikipedia.org/wiki/Taylor_series

    a good rule of thumb is to turn sin and cosine and even e into their taylor series whenever doing limit problems. then subtract whatever you can. and factor out as many x terms as you need to make the top and bottom non zero. and then calculate the limit.
     
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