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Trigonometric Proofs with factor formulae

  1. Feb 26, 2010 #1
    1. The problem statement, all variables and given/known data
    Required to prove that (Sin[A] Sin[2 A] + Sin[3 A] Sin[6 A]) / (Sin[A] Cos[2 A] + Sin[3 A] Cos[6 A]) is identicle to tan[5A]

    2. Relevant equations
    the factor formulae must probably be used.

    3. The attempt at a solution
    I tried using the double angle identities and triple angle identies on top ie i was left with:

    sinA 2sinAcosA + (3sinA - 4sin^3A)(3sinA - 4sin^3A + 3sinA - 4sin^3A)
    then by simplifying i got:
    2sin^2A(cosA + 9 - 24sin^2A + 16sin^4A)
  2. jcsd
  3. Feb 26, 2010 #2


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    Last edited by a moderator: Apr 24, 2017
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