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Homework Help: Prooving Trig Identities

  1. Sep 15, 2006 #1
    the follwing trig identity is used alot...but i am unable to proove it because i dont know wat to start with in solving it....


    it invlves the double angle formulae i know that obviously, i tried substituting sin and cos into the RHS of equation and get my answer down to:

    2sinxcox/(1/cos^2x) which is close...i think since sin2x is 2sinxcosx....

    does any1 hav any ideas??? LOL...hav any ideas...u already know
    appreciate any hints
  2. jcsd
  3. Sep 15, 2006 #2
    damm...evry time i post sumthin on here...i look again at the question and get the answer..soz....

    i ended up with
    (2tanxcos^2x)/(sin^2x+cos^2x) where abviously the bottom = 1 and at the top the cos x's cancel to leave

    2sinxcosx = sin2x

    thanks though
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