The perpendicular from the center of a circle to a chord bisects the chord. Given: A circle with center O, AB is chord of a circle and OC perpendicular from the center O to the chord AB. i.e.    OC ⊥ AB  therefore  ∠OCA and ∠OCB, Both angles are 900.   To prove: AC = CB Construction: join OA and OB.  Proof: In △OCA and △ OCB ∠OCA = ∠OCB […]