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Math Help - Help with sines?

  1. #1
    Newbie
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    Dec 2008
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    Help with sines?

    Obviously, a calculator cannot be used.

    1) cos^-1(tan(37.5))

    2) cos80deg(cos20deg) + sin80deg(sin20deg)

    3) cos(tan^-1(-sqroot3))

    4) The domain and range of tan(cos^-1(x/2)(2))

    5) A formula for cos(30) in terms of cosX alone.

    6) The period of 3cos (5(pi)x + 7)



    Thanks and rep to anyone that solves any of these.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by theqwertykid View Post

    3) cos(tan^-1(-sqroot3))

    \tan(60^{\circ})=\sqrt{3},

    so:

    \tan(120^{\circ})=-\sqrt{3}

    also:

    \tan(300^{\circ})=-\sqrt{3}

    CB
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