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Math Help - [SOLVED] Derivative problem

  1. #1
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    [SOLVED] Derivative problem

    ok, i was doing my hw and i just do not have a clue how to solve this.
    the problem is:
    (2x^3-x)cos(1-x^2)

    and this is what i got or attempted so far. i'm not even sure if this is the right way. can somebody tell me where i went wrong?

    [d/dx(2x^3-x)cos)1-x^2) x (2x^3-x)[d/dx(cos(1-x^2))]
    =(6x^2-1)cos(1-x^2) x 2x(2x^3-x)sin(1-x^2)

    thanks much!
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by katieeej View Post
    ok, i was doing my hw and i just do not have a clue how to solve this.
    the problem is:
    (2x^3-x)cos(1-x^2)

    and this is what i got or attempted so far. i'm not even sure if this is the right way. can somebody tell me where i went wrong?

    [d/dx(2x^3-x)cos)1-x^2) x (2x^3-x)[d/dx(cos(1-x^2))]
    =(6x^2-1)cos(1-x^2) x 2x(2x^3-x)sin(1-x^2)

    thanks much!
    you have to use the product rule, look it up. also note that you need the chain rule to differentiate \cos (1 - x^2), so look that up as well

    y = (2x^3 - x) \cos (1 - x^2)

    \Rightarrow y' = (6x^2 - 1) \cos (1 - x^2) - 2x(2x^3 - x) \sin (1 - x^2)
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