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Lv 5
? asked in Science & MathematicsMathematics · 6 years ago

cos(14pi/3)...?

Can someone explain how cos(14pi/3) requires use of coterminal angles, reference angles, finding co of a special angle and knowing cos in various quadrants?

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  • cidyah
    Lv 7
    6 years ago
    Favorite Answer

    14pi/3 = 4pi + 2pi/3

    cos(14pi/3) = cos(2pi/3)

    2pi/3 lies in quadrant II and the reference angle is pi/3; also , cos is negative in quadrant II

    cos(2pi/3) = -cos(pi/3) = -1/2

  • DWRead
    Lv 7
    6 years ago

    14π/3 > 2π

    14π/3 ≡ 2π/3 mod(2π), so cos(14π/3) = cos(2π/3)

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