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Math Help - Is my 'chain rule' answer correct?

  1. #1
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    Is my 'chain rule' answer correct?

    Hey everyone,

    I was using the product rule to fine the derivative of a problem in my textbook:
    f(x) = sqr root(2+sinx)

    My answer is: -(1/2)cosx(2+sinx)^-(1/2)
    The book answer is: (cosx) / 2 * sqr root(2+sinx)

    Is my answer correct? Is my answer just not simplified?

    Thanks!
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  2. #2
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    Quote Originally Posted by asuastrophysics View Post
    Hey everyone,

    I was using the product rule to fine the derivative of a problem in my textbook:
    f(x) = sqr root(2+sinx)

    My answer is: -(1/2)cosx(2+sinx)^-(1/2)
    The book answer is: (cosx) / 2 * sqr root(2+sinx)

    Is my answer correct? almost ... why the negative sign in front?
    ...
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  3. #3
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    The reason there's a negative sign there is because (from what I know, which isn't much)

    The derivative of sinx is -cosx

    wait...or is it???
    the derivative of cosx is -sinx. maybe I mixed that up.

    The derivative of sinx is just cosx

    If you ignore that small fault, does my answer say the same thing the book answer says?

    Thanks for the fast response btw
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  4. #4
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    get rid of that negative sign, simplify, and see for yourself.
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