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Math Help - Trig Questions !!

  1. #1
    Newbie
    Joined
    Oct 2008
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    20

    Trig Questions !!

    Just gonna use " / " for divided by:

    Express sin2A / 1 - cos 2A in terms of tanA only.

    Express cos 2A - cos(squared)A / 1 + cos2A

    any help at all would be much appreciated !! = )
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  2. #2
    Junior Member
    Joined
    Jul 2008
    Posts
    46
    Hi,

    You might find the following identities useful:

    sin(2x)=2sin(x)cos(x)
    cos(2x)=cos^2(x)-sin^2(x)

    And, of course, tan(x)=sin(x)/cos(x).

    If you use these identities you should be on your way...
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  3. #3
    Banned
    Joined
    Aug 2008
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    \frac{\sin 2A}{1-\cos 2A}

    =\frac{2\sin A \cos A}{2 \sin^2 A}

    =\frac{1}{\tan A}

    use,

    \boxed { \sin 2A =2 \sin A . \cos A =  \frac{2 \tan A}{1 + \tan^2 A}}

    \boxed { \cos 2A = \cos^2 A - \sin^2 A = 2\cos^2 A - 1 = 1 - 2 \sin^2 A = \frac{1-\tan^2 A}{1+\tan^2 A}}
    Last edited by Shyam; October 20th 2008 at 12:46 PM.
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