Cot 81 Degrees

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

What is cot 81°?

Answer

cot 81° ≈
0.1584

Angle in radians: 81° = 9π/20. The point of the angle is in quadrant I, where cotangent is positive.

≈ — rounded to 4 decimal places. An exact form of cot 81° in square roots exists, but it is unwieldy — nested radicals.

cot 81° = cos 81° / sin 81° ≈ 0.1584

xyOP

P(cos 81°, sin 81°) ≈ (0.1564, 0.9877)

C(cot 81°, 1) ≈ (0.1584, 1) — where line OP meets the line y = 1.

All four functions of 81°
FunctionExact valueDecimal
sin 81°—≈ 0.9877
cos 81°—≈ 0.1564
tan 81°—≈ 6.3138
cot 81°—≈ 0.1584

See Also

Recalculate with different values ↑

Cotangent of nearby angles

Anglecot
78°≈ 0.2126
79°≈ 0.1944
80°≈ 0.1763
81°≈ 0.1584
82°≈ 0.1405
83°≈ 0.1228
84°≈ 0.1051

FAQ

What is cot 81°?

cot 81° ≈ 0.1584

Is there an exact value of cot 81°?

Yes: 81° is a multiple of 3°, and the values of such angles can be written with square roots — but the expression is unwieldy, with nested radicals built from the values of 18° and 15° (3° = 18° − 15°). In practice the decimal is used: cot 81° ≈ 0.1584.

Why does a calculator show −1.2331 for cot 81?

The calculator is in radian mode (RAD): it takes cot 81 as the cotangent of 81 radians, cot 81 rad ≈ −1.2331. Switch it to degrees (DEG): cot 81° ≈ 0.1584. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.

See Also