calc

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f(x)=8cos4x

What is the derivative? Im doing online homework and i keep getting an incorrect answer. How do you work out this problem correctly? thanks

  • calc -

    you must know that if
    y = a cos kx, where k is a constant, then
    dy/dx = -a(k)sin kx

    so f(x) = 8cos 4x
    f'(x) = -32sin 4x

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