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Thread: How do you know when to derive using the product rule versus the chain rule?

  1. #1
    Level 16 - Colossus cbil's Avatar
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    How do you know when to derive using the product rule versus the chain rule?

    For example, the function sin^2(3x^2-2x+12). My text says derive using the chain rule, but isn't this simply two things multiplied together, thus calling for the product rule? Is it the fact that sin is squared that makes the chain rule called for?

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  3. #2
    Level 16 - Colossus umupop's Avatar
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    no. it is a function of a function, needing the chaqin rule.
    let g(x) = 3x^2-2x+12
    then this is sin^2(g(x))whose derivative is 2sin(g(x))cos(g(x))g'(x) =
    2sin(g(x))cos(g(x))(6x-2)
    plug the quadratic back in for g(x) and you are done.

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