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Math Help - Derive tan (x/2)

  1. #1
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    Derive tan (x/2)

    The question is: Show that (tan(x/2))' = 1/(1+cos(x)).

    tan(x/2)' = 1/(2(cos (x/2)^2), but I have no idea where to go from here.
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  2. #2
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    cos(x/2)=sqrt((1+cosx)/2)
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  3. #3
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by chickenslowfood View Post
    The question is: Show that (tan(x/2))' = 1/(1+cos(x)).

    tan(x/2)' = 1/(2(cos (x/2)^2), but I have no idea where to go from here.
    You need to know about half angle formula. Look at this:

    List of trigonometric identities - Wikipedia, the free encyclopedia
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  4. #4
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    Solved it now

    Thanks for the help. I bet those half-angle and double-angle formulas might be useful.
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