is the of all the in a that are equidistant from a given point. There are a few particularly notable features of a circle.
- Center - The given point from which all points of the circle are equidistant. Circles are often named by their center point.
- Radius - A that connects the center and any point on the circle. Its length is usually represented algebraically by r.
- Diameter - A segment whose endpoints are on the circle and passes through the center. Its length is usually represented algebraically by d.
- Circumference - The of a circle, usually represented algebraically by C.
In the applet, the center is labeled O.
Therefore, the circle can be referred to as
In any given circle, the lengths of any radius and any diameter are . They are called the
radius and the
diameter of the circle, respectively. To find the and the of a circle with radius r,
their respective are used.
| Formulas for a Circle With Radius r