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Math Help - Cos(2A)

  1. #1
    FJO
    FJO is offline
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    Cos(2A)

    Need help with these questions.

    Let COSA=1/square root of 10


    5.Cos2a

    6.sin2a

    7.cot2a

    8.tan2a
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by FJO View Post
    Need help with these questions.

    Let COSA=1/square root of 10


    5.Cos2a

    6.sin2a

    7.cot2a

    8.tan2a
    here are the identities you need

    \cos 2x = 2 \cos^2 x - 1

    \sin^2 x + \cos^2 x = 1

    \sin 2x = 2 \sin x \cos x

    \cot 2x = \frac {\cos 2x}{\sin 2x}

    \tan 2x = \frac {\sin 2x}{\cos 2x}
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