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Math Help - limit with function

  1. #1
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    limit with function

    hi
    im having trouble with this limit
    ill try my best to display it
    its the function of sin(x-1) over the quadratic x^2 + x - 2
    as x approaches 1

    lim sin(x-1)
    x->1 x^2+x-2
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by chrisc View Post
    hi
    im having trouble with this limit
    ill try my best to display it
    its the function of sin(x-1) over the quadratic x^2 + x - 2
    as x approaches 1

    lim sin(x-1)
    x->1 x^2+x-2
    Please don't double post. See rule #1 here.

    -Dan
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  3. #3
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    before you replied, i already edited my first post and apologized for posting in the wrong section. i didnt look at the specific categories for posting. but i thought I would get better luck posting here then just leaving my question in the elementary tab
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  4. #4
    Math Engineering Student
    Krizalid's Avatar
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    Quote Originally Posted by chrisc View Post
    lim sin(x-1)
    x->1 x^2+x-2
    Well I dunno if someone already helped you, but this is simple, take a look

    \lim_{x\to1}\frac{\sin(x-1)}{(x-1)(x+2)}

    Now define u=x-1, you'll see a well-known limit.
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  5. #5
    Eater of Worlds
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    If you want to take the easy route, you can always use L'Hopital's rule:

    \lim_{x\rightarrow{1}}\frac{sin(x-1)}{x^{2}+x-2}

    Apply the rule by taking derivative of num and den:

    \lim_{x\rightarrow{1}}\frac{cos(x-1)}{2x+1}

    Now, plug in 1 and what's the limit?.
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  6. #6
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    Quote Originally Posted by Krizalid View Post
    Well I dunno if someone already helped you, but this is simple, take a look

    \lim_{x\to1}\frac{\sin(x-1)}{(x-1)(x+2)}

    Now define u=x-1, you'll see a well-known limit.
    thanks a lot (to the both of ya)
    i did the top method, but i had a feeling that this wasn't acceptable (sine being a function)
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