Circumference Of A Circle Formula: A circle consists of all points in a plane that are a given distance, called the radius, from a given point called the center.

#### A segment or line can intersect a circle in several ways.

**•** A segment with endpoints that are the center of the circle and a point of the circle is a **radius**.

**•** A segment with endpoints that lie on the circle is a **chord**.

**•** A chord that contains the circle’s center is a **diameter**.

The circumference of a circle is the distance around the circle.

For a circumference of C units and a diameter of d units or a radius of r units,

**C = π.d** or **C = 2πr**

**Example**: Find the circumference of the circle to the nearest hundredth.

**Answer**: C = 2πr ⇒ Circumference formula

⇒ 2π(13)

≈ 81.68 (Use a calculator)

The circumference is about 81.68 centimeters.