Geometry and TrigonometryVery hardCentral angle from an arc length
Geometry and Trigonometry practice question
An arc of a circle with radius 6 has length 4π. What is the measure, in degrees, of the central angle that subtends the arc?
Answer: 120
The circumference is 12π, and 4π/12π = 1/3 of the circle: (1/3)(360) = 120.
Common wrong answers
- If you answered 4
- 4 is the arc's coefficient of π, not an angle.
- If you answered 60
- 60 uses a circumference of 24π.
- If you answered 240
- 240 doubles 120.
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