2022 · Q58
What is the length of the chord a unit circle which subtends an angle 2θ at the centre, where θ < 45°
Elementary MathematicsTrigonometry
- Asin 2θ
- Bcos 2θ
- C2 sin θ
- D2 cos θ
Explanation
Chord length = 2R sin(central angle/2) = 2x1xsinθ = 2sinθ. The distractor sin2θ forgets to halve the angle. Hence the keyed option is C.