Properties of a Circle
Maths: Edexcel IGCSE Higher, topic 4.5.1
Circle Basics
Radius
- A straight line from the centre of a circle to its edge is called a radius.
Diameter
- A straight line from one side of the circle to the other that passes through the centre is called a diameter.
Circumference
- The circumference of a circle is the distance around the circle, the length of its edge.
Chords in a Circle
A chord is a line that passes from one side of the circle to the other. It doesn't have to go through the middle of the circle.
Splits circumference
- A chord splits the circumference (edge of circle) into two arcs.
- The larger arc is called the major arc and the smaller is called the minor arc.
Splits area
- A chord splits the area of a circle into two parts called segments.
- The larger segment is called the major segment and the smaller one is called the minor segment.
Arc
- When two chords meet at a point, we say the angle x is subtended by the arc between A and C.
Circle Properties
Tangent
- A tangent is a line that just touches the edge of the circle.
Radius meets tangent at a right angle
Sectors
- Two radii split the circle into two parts called sectors.
- The larger sector is called the major sector, the smaller is called the minor sector.
Two radii form an isosceles triangle
- This is because the radii of a circle are always the same length.
Test yourself on Properties of a Circle
What is the name of the red line?
What is the name of the red line?
What is the name of the red line?
What is the name of the straight, dashed blue line?
What is the name of the red line?