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    Cos 100 Degrees

    Sin, Cos, Tan, Cot of an Angle
    Function
    Angle (°)

    What is cos 100°?

    Answer

    cos 100° ≈
    −0.1736

    Angle in radians: 100° = 5π/9. The point of the angle is in quadrant II, where cosine is negative.

    ≈ — rounded to 4 decimal places. cos 100° can't be written with square roots: 100° is not a multiple of 3°.

    cos 100° = cos(180° − 80°) = −cos 80° ≈ −0.1736

    P(cos 100°, sin 100°) ≈ (−0.1736, 0.9848)

    xyOP

    P(cos 100°, sin 100°) ≈ (−0.1736, 0.9848)

    Highlighted: the projection on the x-axis — cosine, x ≈ −0.1736.

    All four functions of 100°
    FunctionExact valueDecimal
    sin 100°—≈ 0.9848
    cos 100°—≈ −0.1736
    tan 100°—≈ −5.6713
    cot 100°—≈ −0.1763

    Reference angle: cos 80° ≈ 0.1736

    See Also

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    https://calculat.io/en/number/trigonometry/cos--100Copy
    <a href="https://calculat.io/en/number/trigonometry/cos--100">Cos 100 Degrees: Cosine of 100° on the Unit Circle</a>Copy
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    Cos 100 Degrees: Cosine of 100° on the Unit Circle. cos 100° ≈ −0.1736. The cosine is the x-coordinate of the point at 100° on the unit circle; 100° reduces to 80°.
    https://calculat.io/en/number/trigonometry/cos--100/generated.jpgCopy

    Cosine of nearby angles

    Anglecos
    90°0
    97°≈ −0.1219
    98°≈ −0.1392
    100°≈ −0.1736
    101°≈ −0.1908
    105°−(√6 − √2)/4
    106°≈ −0.2756
    Recalculate with different values ↑

    FAQ

    What is cos 100°?

    cos 100° ≈ −0.1736

    Why does cos 100° have no exact value?

    A trigonometric value of a whole number of degrees can be written with square roots only when the angle is a multiple of 3°. 100° is not, so no such exact form exists; the value is used as a decimal: cos 100° ≈ −0.1736.

    Why does a calculator show 0.8623 for cos 100?

    The calculator is in radian mode (RAD): it takes cos 100 as the cosine of 100 radians, cos 100 rad ≈ 0.8623. Switch it to degrees (DEG): cos 100° ≈ −0.1736. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.

    See Also