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Homework Help: Verifying trig identity

  1. Oct 27, 2009 #1
    1. The problem statement, all variables and given/known data

    (sin 3α/sin α) - (cos 3α/cosα) =2

    2. Relevant equations

    3. The attempt at a solution

    I know for sin 2 α I would put 2 sinαcosα, so for 3α, do I just put 3sinαcosα?
    for cos 3α, I'm sorta clueless because there's 3 we can use for cosine,
    Then after that step, I know to get both of them on the LHS to have a common denominator, which sinα cosα, please help. Thank yyou in advance!
  2. jcsd
  3. Oct 27, 2009 #2


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    Homework Helper
    Education Advisor
    Gold Member

    Start with the angle-sum formulas.
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