🔸 Concept 9: Angle at Center and Subtended Angle

If the central angle \( \angle AOB = 2\theta \), then the angle at the circumference \( \angle ACB = \theta \).

Also, \( \angle ADB = 180^\circ - \theta \) lies in the opposite arc.

🔸 Concept 10: Complete Angle Diagram from Chord

A chord creates angles on both sides of a circle. For angle \( \theta \) at the top, the angle at the base becomes \( 180^\circ - \theta \).