Circle theorems are some properties of a circle. There are mainly circle theorems.
Theorem 1: Angle at the center: The angle subtended at the center by two points on the circle is twice the angle subtended by it on any point on the circumference of the circle
Theorem 2: Angle in a semi-circle: The angle made at the circumference of a semi-circle is a right angle.
Theorem 3: Angles in the same segment: The angle subtended by the same arc on the circumference of a circle is equal.
Theorem 4: Angles in a Cyclic quadrilateral: The sum of opposite angles in a cyclic quadrilateral is .
Theorem 5: Tangent-Radius theorem: A line is tangent to the circle only if it is perpendicular to the radius drawn to the point of tangency.
Theorem 6:Tangent from a point to the circle: If tangents are drawn from a point to the circle, then the length of the tangents will be equal.
Theorem 7: If tangents are drawn from a point to the circle, the line joining the center and the point bisects the angle included by tangents.
Theorem 8: Alternate segment theorem: The angle formed between the tangent and the chord through the point of contact of the tangent is equal to the angle formed by the chord in the alternate segment.
