- The Geometry of CirclePerpendicular from Centre Bisects ChordEqual Chord Equal Distance from CentreAngle at Centre and Angle at CircumferenceAngles in the Same SegmentEqual Arcs Equal Chords Equal AnglesCyclic QuadrilateralTest for Concyclic Points (1)Test for Concyclic points (2)Tangent and RadiusTangent from External PointAngle in Alternate Segment