Circle Theorems

• Alternate segment theorem

  
• angle at the centre theorem

  
• Angles in the same segment theorem

  
• The angle in a semi circle is 90 degrees

  
• The perpendicular from the centre to the circumference bisects the chord into two equal parts

  
• The opposite angles in a cyclical quadrilateral add up to 180 degrees

  
• Diagram A?

  The angle between a tangent and radius is 90 degrees

  Diagram B

  Tangents which meet at the same point are equal in length