Discovering Circles

A circle is a set of points in a plane that are all the same distance from a center point. This distance is called the radius.

Key Elements

• Radius: Distance from center to any point on the circle.
• Diameter: Distance across the circle through the center (\(2 \times \text{radius}\)).
• Circumference: The perimeter of the circle.
• Pi (\(\pi\)): The ratio of the circumference to the diameter, approximately 3.14159.

Important Formulas

• Circumference: \(C = 2\pi r\)
• Area: \(A = \pi r^2\)

Where Do We See Circles?

Circles appear in wheels, coins, clocks, and many sports (basketballs, soccer balls). Their symmetry makes them important in engineering and design.