A circle is the set of all points in a plane that are at a given distance from a center point.
| Parameter | Formula | Description |
|---|---|---|
| Radius | r | Distance from center to any point on the circle |
| Diameter | d = 2r | Twice the radius, longest chord through center |
| Circumference | C = 2πr | Distance around the circle |
| Area | S = πr² | Area enclosed by the circle |
Diameter: d = 2 · 5 = 10 cm
Circumference: C = 2π · 5 = 10π ≈ 31.416 cm
Area: S = π · 5² = 25π ≈ 78.540 cm²
The constant π (pi) ≈ 3.14159265359... is the ratio of a circle's circumference to its diameter. It is an irrational number, meaning its decimal representation never ends and never repeats.
All circles are similar to each other — they have the same shape regardless of size.