Circle Theorem

The Circle Theorem states that in a circle, angles related to the diameter or arcs have special properties. For example, an angle inscribed in a semicircle (where the endpoints are on the diameter) is always a right angle (90°). Also, angles subtended by the same arc at the circumference are equal, and angles opposite each other in a cyclic quadrilateral (a four-sided figure inside the circle) sum to 180°. These principles help understand how angles and arcs interact within a circle, revealing consistent relationships that simplify solving geometric problems involving circles.