4.5.1

Properties of a Circle

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Circle Basics

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Radius

  • A straight line from the centre of a circle to its edge is called a radius.
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Diameter

  • A straight line from one side of the circle to the other that passes through the centre is called a diameter.
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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.

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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.
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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.
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Arc

  • When two chords meet at a point, we say the angle x is subtended by the arc between A and C.

Circle Properties

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Tangent

  • A tangent is a line that just touches the edge of the circle.
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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.
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Two radii form an isosceles triangle

  • This is because the radii of a circle are always the same length.

Jump to other topics

1Numbers

2Equations, Formulae & Identities

3Sequences, Functions & Graphs

4Geometry

5Vectors & Transformation Geometry

6Statistics & Probability

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