Geometry and TrigonometryVery hardArc length from a central angle
Geometry and Trigonometry practice question
A circle has radius 9. What is the length of an arc of the circle that is cut off by a central angle of 120°?
- A. 6πCorrect
- B. 3π
- C. 12π
- D. 27π
Answer: A. 6π
The circumference is 18π, and 120° is one third of the circle: 6π.
Why the other answers are wrong
- B. 3π
- 3π is one sixth of the circumference.
- C. 12π
- 12π is two thirds of the circumference.
- D. 27π
- 27π is the area of the sector, not the arc length.
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