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Math Help - AP practice question

  1. #1
    Super Member bigwave's Avatar
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    Cool AP practice question

    If f(u) = \sin{u} and u = g(x) = x^2-9, then  (f \circ g)'(3) =

    I know that g'(x)= 2x but didn't know how to use this,
    the answer is 6
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  2. #2
    Junior Member
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    you got this : f composition g = sin(x^2-9) finding it's derivative you get this ..
    cos(x^2-9)*2x ,substituting 3 yields cos(9-9)*2*3=1*6=6
    gl
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  3. #3
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by bigwave View Post
    If f(u) = \sin{u} and u = g(x) = x^2-9, then  (f \circ g)'(3) =

    I know that g'(x)= 2x but didn't know how to use this,
    the answer is 6
    So,

    (f \circ g)=\sin{(x^{2}-9)}

    (f \circ g)' = \cos{(x^{2}-9)} \times 2x
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