GCSE Maths

• The angle subtended by an arc at the centre is twice the angle subtended at the circumference

  
• The angles at the circumference subtended by the same arc are equal

  
• Opposite angles in a cyclic quadrilateral add up to 180°.

  
• The angle at the circumference in a semicircle is a right angle.

  
• A radius meets a tangent at 90°

  
• Tangents which meet at the same point are equal in length

  
• A radius meets a chord at 90°

  
• The angle between a tangent and a chord is equal to the angle in the alternate segment

  Alternate segment theorem

  
• Angles on parallel lines

  A) Corresponding angles

  B) Co-interior angles

  C) Alternate Angles

  D) Vertically opposite angles