Cos 140 Degrees

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

What is cos 140°?

Answer

cos 140° ≈
−0.7660

Angle in radians: 140° = 7π/9. The point of the angle is in quadrant II, where cosine is negative.

≈ — rounded to 4 decimal places. cos 140° can't be written with square roots: 140° is not a multiple of 3°.

cos 140° = cos(180° − 40°) = −cos 40° ≈ −0.7660

P(cos 140°, sin 140°) ≈ (−0.7660, 0.6428)

xyOP

P(cos 140°, sin 140°) ≈ (−0.7660, 0.6428)

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

All four functions of 140°
FunctionExact valueDecimal
sin 140°—≈ 0.6428
cos 140°—≈ −0.7660
tan 140°—≈ −0.8391
cot 140°—≈ −1.1918

Reference angle: cos 40° ≈ 0.7660

See Also

Recalculate with different values ↑

Cosine of nearby angles

Anglecos
130°≈ −0.6428
134°≈ −0.6947
135°−√2/2
140°≈ −0.7660
142°≈ −0.7880
144°−(√5 + 1)/4
145°≈ −0.8192

FAQ

What is cos 140°?

cos 140° ≈ −0.7660

Why does cos 140° 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°. 140° is not, so no such exact form exists; the value is used as a decimal: cos 140° ≈ −0.7660.

Why does a calculator show −0.1978 for cos 140?

The calculator is in radian mode (RAD): it takes cos 140 as the cosine of 140 radians, cos 140 rad ≈ −0.1978. Switch it to degrees (DEG): cos 140° ≈ −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