All Topics
Geometry
Circles
圆
What to Study
- Area (πr²)
- Circumference (2πr)
- Arc length
- Sector area
- Central angles
Key Formulas
Area = πr²
Circumference = 2πr = πd
Full circle = 360°
Arc length = (θ/360) × 2πr
Sector area = (θ/360) × πr²