Circles Concepts

Understanding the Concepts of Circles

Circle is one of the 2D foundational concepts that will help us address higher level geometry and mensuration problems. The key topics in circles to learn are radius, chord, diameter, circumference, area, arc, segment and sector.

The following visual representation can be used to demonstrate the concepts of circles:

Let us understand the meaning of these terms one by one.

1. Radius

The radius of a circle is the distance between its centre and its outside edge. It is represented by the symbol r.

2. Chord

A chord is a line segment that connects two locations on the circumference of a circle.

3. Diameter

The chord that runs through the centre of a circle is known as its diameter. It's also the longest chord within a circle. The length of the diameter is equal to two times the radius and is denoted by the letter D

Diameter = 2r

4. Circumference

It is the perimeter of a circle, and it has been empirically discovered that circumference divided by diameter yields a constant number, which is symbolised as **pi (**π). Its value is approximately equal to 3.14, from which we can develop a formula to get the circumference of a circle.

Circumference = 2 π r

5. Area

Area is the total surface covered inside a circle. It's defined by the formula π*(r^2)

6. Arc

An arc is a portion or segment of a circle's circumference. The sector is the section of a circle bounded by two radii and an arc.

7. Segment

A segment is the space surrounded by the chord and the corresponding arc in a circle. 2 types of segments.

• Minor segment
• Major segment

8. Sector

A sector is created by connecting the ends of an arc to the centre.

When the endpoints are connected to the centre, two sectors are formed: Minor and Major. Unless otherwise specified, we exclusively consider the Minor sector by design.