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    Cos 40 Degrees

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

    What is cos 40°?

    Answer

    cos 40° ≈
    0.7660

    Angle in radians: 40° = 2π/9. The point of the angle is in quadrant I, where cosine is positive.

    ≈ — rounded to 4 decimal places. cos 40° can't be written with square roots: 40° is not a multiple of 3°.

    P(cos 40°, sin 40°) ≈ (0.7660, 0.6428)

    xyOP

    P(cos 40°, sin 40°) ≈ (0.7660, 0.6428)

    Highlighted: the projection on the x-axis — cosine, x ≈ 0.7660.

    All four functions of 40°
    FunctionExact valueDecimal
    sin 40°—≈ 0.6428
    cos 40°—≈ 0.7660
    tan 40°—≈ 0.8391
    cot 40°—≈ 1.1918

    See Also

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    https://calculat.io/en/number/trigonometry/cos--40Copy
    <a href="https://calculat.io/en/number/trigonometry/cos--40">Cos 40 Degrees: Cosine of 40° on the Unit Circle</a>Copy
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    Cos 40 Degrees: Cosine of 40° on the Unit Circle. cos 40° ≈ 0.7660. The cosine is the x-coordinate of the point at 40° on the unit circle.
    https://calculat.io/en/number/trigonometry/cos--40/generated.jpgCopy

    Cosine of nearby angles

    Anglecos
    37°≈ 0.7986
    38°≈ 0.7880
    39°≈ 0.7771
    40°≈ 0.7660
    41°≈ 0.7547
    42°≈ 0.7431
    43°≈ 0.7314
    Recalculate with different values ↑

    FAQ

    What is cos 40°?

    cos 40° ≈ 0.7660

    Why does cos 40° 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°. 40° is not, so no such exact form exists; the value is used as a decimal: cos 40° ≈ 0.7660.

    Why does a calculator show −0.6669 for cos 40?

    The calculator is in radian mode (RAD): it takes cos 40 as the cosine of 40 radians, cos 40 rad ≈ −0.6669. Switch it to degrees (DEG): cos 40° ≈ 0.7660. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.

    See Also