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Math Help - sec and cot

  1. #1
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    sec and cot

    Evaluate: sec600 + cot315 Do not use a calculator.
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by robinpatrick View Post
    Evaluate: sec600 + cot315 Do not use a calculator.
    600 degrees is the same thing as -120 degrees (600=360*2-120), now
    sec(600) = 1/cos(-120) = 1/cos(120) = -1/cos(60) =-2/sqrt(3)

    (you are expected to know that cos(60)=sqrt(3)/2)

    315 degrees is the same thing as -45 degrees (315=360-45), now
    cot(315) = cot(-45) = 1/tan(-45) = -1/tan(45) = -1

    (you are expected to know that tan(45) = 1).

    so:

    sec(600) + cot(315) = 2/sqrt(3) - 1.

    RonL
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