Properties of Circles (Edexcel GCSE Maths: Foundation)

What terms related to circles do I need to know?

• Circles have several specific terms that you need to be familiar with:
  • A circle's perimeter is called a circumference
  • Its line of symmetry is called a diameter
  • The line from the centre of the circle to its circumference is called a radius
    • The diameter is equal to 2 × the radius
  • A portion of the circumference is called an arc
  • A portion of the area, contained between two radii and an arc, is called a sector
  • A line between two points on the circumference is called a chord
  • The area formed between a chord and an arc is called a segment
  • A line which intersects the circumference at one point only, is called a tangent

• The ratio  is equal to π (3.14159...)