Equal chords of a circle subtend equal angles at the center. Given:  Two equal chords AB and CD of a circle with center O. i,e. AB = CD. To prove: ∠AOB = ∠COD Proof:  In △AOB and △ COD OA = OC (Radius of circle)OB = OD (Radius of circle)AB = CD  (Given) Hence, △AOB ≅ △ COD (SSS Congruence rule)     ∴   ∠AOB […]