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Math Help - Solve this identity

  1. #1
    Newbie
    Joined
    May 2008
    Posts
    8

    Solve this identity

    Looking for some help!!!

    Have been asked to solve the following:

    "If sin13=p and cos12 = q express sin 25 in terms of p and q."

    Have got this far

    sin25
    = sin (13+12)
    = sin13cos12 + cos13sin12
    = p.q + ?

    Now what ?

    All ideas welcomed

    Thanks
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by statsnewbie View Post
    Looking for some help!!!

    Have been asked to solve the following:

    "If sin13=p and cos12 = q express sin 25 in terms of p and q."

    Have got this far

    sin25
    = sin (13+12)
    = sin13cos12 + cos13sin12
    = p.q + ?

    Now what ?

    All ideas welcomed

    Thanks
    pfft. I guess you could use that \cos x = \pm \sqrt{1 - \sin^2 x} and \sin x = \pm \sqrt {1 - \cos^2 x}

    take the appropriate signs based on what quadrant you are in
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