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Lim x->1 (sin (x^2 - 1) / (x-1)?

I need to see the step by step work for this. I looked it up on wolfram alpha, and it says the limit is 2, but we haven't learned L'Hospital's rule yet, so I can't use the step by step on wolfram alpha. Could you help please?

1 Answer

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  • kb
    Lv 7
    9 years ago
    Favorite Answer

    Use lim(t→0) sin(t)/t = 1 as follows:

    lim(x→1) sin(x^2 - 1)/(x - 1)

    = lim(x→1) (x + 1) * sin(x^2 - 1)/[(x + 1) * (x - 1)]

    = lim(x→1) (x + 1) * sin(x^2 - 1)/(x^2 - 1)

    = lim(x→1) (x + 1) * lim(x→1) sin(x^2 - 1)/(x^2 - 1)

    = lim(x→1) (x + 1) * lim(t→0) sin(t)/t, letting t = x^2 - 1

    = 2 * 1

    = 2.

    I hope this helps!

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