the degrees of a circle
What do you like best about circles? We like their perfectly round shapes. They don't have those pointy ends you'll find on squares and triangles. Some of our favorite things are shaped like circles. For example, our favorite dessert — pie — is shaped like a circle. And so is our favorite toy: the hula hoop.
What other circle-shaped things do you see or use every day? Geometry teachers define a circle as the set of points on a plane that are all the exact same distance from a central point. This means that circles are flat. When you study circles, you learn that every circle has a radius, a diameter, a circumference, and an area.
A circle's radius is the distance from its center to its edge. A circle's diameter is the distance across the circle at its widest point. The diameter of a circle is always exactly twice its radius. A circle's perimeter — the distance all the way around its edge — is called its circumference. To calculate the circumference of a circle, you need to know its radius.
