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Math Help - Finding the value of a derivative

  1. #1
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    Finding the value of a derivative

    Find the value of the derivative of the function at (╥, -1)
    Function: g(t) = 2 + 3 cos t

    My work:
    Plugged in ╥ to t
    2 + 3 cos (╥)

    Then I turn it into g' (g prime)
    The rule is usually multiply the exponent into the coefficient than minus one from the exponent.
    For example y = 4x^2 + 4x + 1
    y' = 8x + 4

    Can anyone help me with 2 + 3 cos t.

    Thanks!
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Finding the value of a derivative

    You want to differentiate first, then evaluate the derivative at t=\pi.

    Do you know how to differentiate the cosine function?
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  3. #3
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    Re: Finding the value of a derivative

    Quote Originally Posted by MarkFL2 View Post
    You want to differentiate first, then evaluate the derivative at t=\pi.

    Do you know how to differentiate the cosine function?
    Oh! Doesn't cos becomes -sin then.
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: Finding the value of a derivative

    Yes, so you have:

    g'(t)=-3\sin(t)

    Now, you may evaluate the derivative for t=\pi.
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