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Homework Help: Need help with limit question

  1. Oct 2, 2006 #1
    ok, so today we had our calc midterm, and on it was this question:

    the limit as X->0 of (1-cosx)/(x^2)

    what i did was multiply the top and bottom with the conjugate of (1-cosx) which is (1+cosx). then i managed to factor out (sinx/x) twice. since (sinx/x) is just one, iarrived at the answer of 0.5 for the limit of this question.

    some of my friends tell me that limit does not exist, because the (X^2) would evaluate to zero and you cant have a zero in the denominator.

    so who's right?
  2. jcsd
  3. Oct 2, 2006 #2
    you are right. [tex] \lim_{x\rightarrow 0 } \frac{1-\cos^{2}x}{x^{2}(1+\cos x)} = \frac{\sin^{2}x}{x^{2}(1+\cos x)} = \frac{\sin x}{x} \frac{\sin x}{x}\frac{1}{1+\cos x} = \frac{1}{2} [/tex]
    Last edited: Oct 2, 2006
  4. Oct 2, 2006 #3
    yes! thank you.
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