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Math Help - Prove Trig Identity

  1. #1
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    Prove Trig Identity

    Prove

    cot z -32 cot 32 z = - log cos16 z x cos 8 z x cos 4z x co2z x cos z
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  2. #2
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    Re: Prove Trig Identity

    Quote Originally Posted by JoeHus View Post
    Prove cot z -32 cot 32 z = - log cos16 z x cos 8 z x cos 4z x co2z x cos z
    As far as I can tell, your post is completely meaningless,
    You need to tell us if z is a complex variable?
    Do you know the definition of the complex function $\cot(z)~?$
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  3. #3
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    Re: Prove Trig Identity

    Sorry for not replying as I lost my details due to a computer crash.

    Z is not a complex variable and yes I do know the definition of the complex function cot Z.
    The above identity was from an exam question for A-Levels passed to me and the full context of the question was
    Prove
    tan z + 2 tan2z + 4 tan4z +8 tan8z + 16tan16z=cot z -32 cot 32 z

    I only posted part of the question which included a hint from someone: to work on right hand side by integrating it and expanding it to - log cos16 z x cos 8 z x cos 4z x co2z x cos z and finally differentiating it.
    The differentiation part is easy and immediately results in the left hand side answer, no problem.
    Integrating results in a ln sinz etc , but the expansion is not so easy.
    regards
    JoeHR
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