EDEXCEL GCSE FOUNDATION MATHS - What are Parts of the Circle

Edexcel GCSE Foundation Maths: Parts of a Circle

This tutorial will introduce you to the key parts of a circle and their definitions.

Key Parts of a Circle

• Centre (O): The point that is exactly in the middle of the circle. All points on the circle are the same distance from the centre.
• Radius (r): A line segment from the centre of the circle to any point on the circle.
• Diameter (d): A line segment that passes through the centre of the circle and has both endpoints on the circle. It is twice the length of the radius (d = 2r).
• Circumference (C): The distance around the outside of the circle.
• Chord: A line segment that connects two points on the circle.
• Arc: A portion of the circumference of the circle.
• Sector: A region of the circle bounded by two radii and an arc.
• Segment: A region of the circle bounded by a chord and an arc.

Diagram

       O
      / \
     /   \
    /     \
   /_______\
  *--------*

   A        B

In the diagram above:

• O is the centre of the circle.
• OA and OB are radii.
• AB is a diameter.
• ACB is an arc.
• OAB is a sector.
• ACB is a segment.

Key Formulas

• Circumference (C) = ?d = 2?r (where ? ? 3.14)

Example

Find the circumference of a circle with a radius of 5 cm.

Using the formula:

C = 2?r C = 2 × 3.14 × 5 cm C = 31.4 cm

Therefore, the circumference of the circle is 31.4 cm.

Practice

1. Draw a circle and label its centre, radius, and diameter.
2. What is the relationship between the radius and the diameter of a circle?
3. A circle has a diameter of 12 cm. What is its circumference?

By understanding the different parts of a circle and their definitions, you will be able to solve various geometry problems related to circles.