Tan 198 Degrees
Sin, Cos, Tan, Cot of an Angle
What is tan 198°?
Answer
tan 198° =
√(25 − 10√5)/5 ≈ 0.3249
Angle in radians: 198° = 11π/10. The point of the angle is in quadrant III, where tangent is positive.
≈ — rounded to 4 decimal places.
tan 198° = tan(180° + 18°) = tan 18° = √(25 − 10√5)/5
tan 198° = sin 198° / cos 198° = (−(√5 − 1)/4) / (−√(10 + 2√5)/4) = √(25 − 10√5)/5
Regular pentagon (golden ratio): cos 36° = (√5 + 1)/4.
tan 18° = sin 18° / cos 18° = √(25 − 10√5)/5
P(cos 198°, sin 198°) ≈ (−0.9511, −0.3090)
T(1, tan 198°) ≈ (1, 0.3249) — where line OP meets the line x = 1, on the extension of the ray beyond O (dashed).
| Function | Exact value | Decimal |
|---|---|---|
| sin 198° | −(√5 − 1)/4 | ≈ −0.3090 |
| cos 198° | −√(10 + 2√5)/4 | ≈ −0.9511 |
| tan 198° | √(25 − 10√5)/5 | ≈ 0.3249 |
| cot 198° | √(5 + 2√5) | ≈ 3.0777 |
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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
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