1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    Science Advisor
    Homework Helper

    Last edited by a moderator: Apr 24, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Trigonometric Proofs with factor formulae
  1. Trigonometric Proof (Replies: 5)

  2. Factor Formulae (Replies: 1)

  3. Trigonometric proof (Replies: 8)