- Circle Theorems
- Angles off the diameter in a semicircle= 90 degrees
- Angles in the same segment off a chord are equal.
- Angle at a centre is twice angle formed at circumference in same segment off a chord.
- Opposite angles of a cyclic quadrilateral add up to 180 degrees
- Angles of a tangent to the radius equals to 90 degrees
- Alternate segment theorem: angle between chord and tangent= angle in alternate segment
- Intersecting chords: AP*PB=CP*CD