Tan 81 Degrees
Sin, Cos, Tan, Cot of an Angle
What is tan 81°?
Answer
tan 81° ≈
6.3138
Angle in radians: 81° = 9π/20. The point of the angle is in quadrant I, where tangent is positive.
≈ — rounded to 4 decimal places. An exact form of tan 81° in square roots exists, but it is unwieldy — nested radicals.
tan 81° = sin 81° / cos 81° ≈ 6.3138
P(cos 81°, sin 81°) ≈ (0.1564, 0.9877)
T(1, tan 81°) ≈ (1, 6.3138) — where line OP meets the line x = 1; T is beyond the drawing, the arrow points to it.
See Also
- Arcsin, Arccos, Arctan, Arccot - The angle from the value of its sine, cosine, tangent or cotangent: exact in degrees and π, with the check and the unit circle
- Square Root Calculator - Calculate the square root of any number
- Simplify Square Root Calculator - Write any square root in simplest radical form, step by step
- Geometry Formulas: Area, Volume, Perimeter - The formula for every standard shape, where it comes from, and worked examples
Tangent of nearby angles
FAQ
What is tan 81°?
tan 81° ≈ 6.3138
Is there an exact value of tan 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: tan 81° ≈ 6.3138.
Why does a calculator show −0.8110 for tan 81?
The calculator is in radian mode (RAD): it takes tan 81 as the tangent of 81 radians, tan 81 rad ≈ −0.8110. Switch it to degrees (DEG): tan 81° ≈ 6.3138. In radians the value is never undefined: π is irrational, so a whole number of radians never lands exactly on an axis.
See Also
- Tan 71 Degrees: Tangent of 71° on the Unit Circle
- Tan 72 Degrees: Tangent of 72° on the Unit Circle
- Tan 73 Degrees: Tangent of 73° on the Unit Circle
- Tan 74 Degrees: Tangent of 74° on the Unit Circle
- Tan 75 Degrees: Tangent of 75° on the Unit Circle
- Tan 76 Degrees: Tangent of 76° on the Unit Circle
- Tan 77 Degrees: Tangent of 77° on the Unit Circle
- Tan 78 Degrees: Tangent of 78° on the Unit Circle
- Tan 79 Degrees: Tangent of 79° on the Unit Circle
- Tan 80 Degrees: Tangent of 80° on the Unit Circle
- Tan 82 Degrees: Tangent of 82° on the Unit Circle
- Tan 83 Degrees: Tangent of 83° on the Unit Circle
- Tan 84 Degrees: Tangent of 84° on the Unit Circle
- Tan 85 Degrees: Tangent of 85° on the Unit Circle
- Tan 86 Degrees: Tangent of 86° on the Unit Circle
- Tan 87 Degrees: Tangent of 87° on the Unit Circle
- Tan 88 Degrees: Tangent of 88° on the Unit Circle
- Tan 89 Degrees: Tangent of 89° on the Unit Circle
- Tan 90 Degrees: Tangent of 90° on the Unit Circle
- Tan 97 Degrees: Tangent of 97° on the Unit Circle
- Тангенс 81 градуса (tg 81°) на единичной окружности
- Tangente de 81 grados (tan 81°) en el círculo unitario
- Tangente de 81 graus (tg 81°) no ciclo trigonométrico