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Limits problem

  1. Sep 2, 2010 #1
    1. The problem statement, all variables and given/known data

    [PLAIN]http://img137.imageshack.us/img137/4242/probhr.jpg [Broken]


    Well ,my problem is why after substitution for the first time the result os uncertainity (0/0)

    Is X=0?

    and I don't understand the step no 2
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 2, 2010 #2

    vela

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    What you've written doesn't make sense.
     
  4. Sep 2, 2010 #3
    so.....?
     
  5. Sep 2, 2010 #4

    Dick

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    I think they mean the symbol you are writing as 'A' to be the symbol for pi.
     
  6. Sep 2, 2010 #5

    vela

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    Go back and check that you accurately copied the original problem and the solution. It's pointless to try explain something that is wrong to begin with.
     
  7. Sep 2, 2010 #6
    awww you are right.The problem was written in another language so I translated it in a wrong way...I'll try to solve it again

    Thanks for all of you
     
  8. Sep 3, 2010 #7
    Ok..I'm back
    so I know that sin(180-x)=sin(pi-x)

    but x= pi right?
    so sin(pi-x) = sin (x-pi) ?
    why did we use sin(pi-x) instead ?
    hope u could understand me
    thanks
     
  9. Sep 3, 2010 #8

    Dick

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    x doesn't equal pi. But for any x, sin(x)=sin(pi-x)=(-sin(x-pi)). Look at graph of the sin function or use a sin addition formula to prove that. They are using those identities to prove the limit.
     
  10. Sep 3, 2010 #9
    so why not?
    isn't x-pi=0 as mentioned in the problem ?
     
  11. Sep 3, 2010 #10

    Dick

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    x-pi->0. That means x approaches pi (gets closer and closer to pi). It's not equal to pi. If x=pi then you have a zero in the denominator and the ratio is undefined.
     
  12. Sep 3, 2010 #11
    oh ok thanks very much
     
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