- Circle TheoremsIsosceles Triangle in a Circle (page 1)Isosceles Triangle in a Circle (page 2)Simple Angle in a Semi-circleAngle in a semi-circleAngle in a semi-circle (proof)Simple Angle at the CentreSimple Angle at the Centre (Reflex Case)Angle at the centre (page 1)Angle at the centre (page 2)Angle at the centre (page 3)Angle at the centre (page 4)Angles in the same SegmentAngles in the same Segment (Proof)Simple Cyclic QuadrilateralCyclic Quadrilateral (Proof)Alternate Segment Theorem (page 1)Alternate Segment Theorem (page 2)Alternate Segment Theorem (proof)Common Tangents to a CircleCommon Tangents to a Circle (Proof)