Brainlag PlusArc length, sector area and sector perimeter from the angle, and working back to the angle or the radius.
A sector is a fraction of a circle
A sector with angle θ at the centre is θ/360 of the whole circle.
So take that fraction of the circumference, or of the area.
arc length = θ/360 × 2πr
sector area = θ/360 × πr²
Not drawn accurately
- arc = 80/360 × 2 × π × 6 = 8.3775... = 8.38 cm (3 s.f.)
- area = 80/360 × π × 6² = 25.132... = 25.1 cm² (3 s.f.)
- perimeter = 8.3775... + 6 + 6 = 20.4 cm (3 s.f.)
The rest of this lesson and its 7 practice questions are in Plus.
Screen 1 of 3, free to read.
- 7 exam-style questions, marked as you go, each with a worked solution
- The Scientific Calculator beside every question
- Anything you get wrong is saved to your flashcards