3.2.5

Circle Theorems - Angle at the Centre

Test yourself

Circle Theorems

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Proof

  • Split the shape into two isosceles triangles and label the angles.
  • The angle at the centre is 360° - x - y and the angle at the circumference is a + b.
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Proof continued

  • Since the angles in a triangle add up to 180°:
    a = 12(180° - y), b = 12(180° - x)
  • So angle at circumference = a + b = 12(360° - x - y)
    = 12 × angle at centre.

Jump to other topics

1Proof

2Algebra & Functions

2.1Powers & Roots

2.2Quadratic Equations

2.3Inequalities

2.4Polynomials

2.5Graphs

2.6Functions

2.7Transformation of Graphs

2.8Partial Fractions (A2 Only)

3Coordinate Geometry

4Sequences & Series

5Trigonometry

6Exponentials & Logarithms

7Differentiation

8Integration

9Numerical Methods

10Vectors

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