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Math Help - derivative

  1. #1
    Newbie Foxtenn5's Avatar
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    Question derivative

    Hi everyone...

    Could someone help me find the derivative of ln(2cosx) ? So far, I have
    (1/2cosx)(-2sinx), so (-2sinx/2cosx). Is this right???

    I would appreciate all the help I can get!
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  2. #2
    Super Member flyingsquirrel's Avatar
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    Hi

    Yes, it's correct. Get rid off the two 2 and give your answer using \tan x and it'd be perfect.
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  3. #3
    Newbie Foxtenn5's Avatar
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    Is it negative?

    Oh, thank you! Would it be -tanx?
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  4. #4
    MHF Contributor
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    Quote Originally Posted by Foxtenn5 View Post
    Hi everyone...

    Could someone help me find the derivative of ln(2cosx) ? So far, I have
    (1/2cosx)(-2sinx), so (-2sinx/2cosx). Is this right???

    I would appreciate all the help I can get!
    Yes, you have solved the problem correctly. Alternatively, you could break up the expression to \ln{2} + \ln{(\cos x)} and then differentiate. Either way, the 2 isn't going to change the result of -\tan {x}.
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