Sin 80 Degrees

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

What is sin 80°?

Answer

sin 80° ≈
0.9848

Angle in radians: 80° = 4π/9. The point of the angle is in quadrant I, where sine is positive.

≈ — rounded to 4 decimal places. sin 80° can't be written with square roots: 80° is not a multiple of 3°.

P(cos 80°, sin 80°) ≈ (0.1736, 0.9848)

xyOP

P(cos 80°, sin 80°) ≈ (0.1736, 0.9848)

Highlighted: the projection on the y-axis — sine, y ≈ 0.9848.

All four functions of 80°
FunctionExact valueDecimal
sin 80°—≈ 0.9848
cos 80°—≈ 0.1736
tan 80°—≈ 5.6713
cot 80°—≈ 0.1763

See Also

Recalculate with different values ↑

Sine of nearby angles

Anglesin
77°≈ 0.9744
78°≈ 0.9781
79°≈ 0.9816
80°≈ 0.9848
81°≈ 0.9877
82°≈ 0.9903
83°≈ 0.9925

FAQ

What is sin 80°?

sin 80° ≈ 0.9848

Why does sin 80° 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°. 80° is not, so no such exact form exists; the value is used as a decimal: sin 80° ≈ 0.9848.

Why does a calculator show −0.9939 for sin 80?

The calculator is in radian mode (RAD): it takes sin 80 as the sine of 80 radians, sin 80 rad ≈ −0.9939. Switch it to degrees (DEG): sin 80° ≈ 0.9848. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.

See Also