Geometry Practice Test 2

OA = OB = OC = radius
∠BOC = 2 ∠BAC
∠BOC = 170°

ΔBOD and ΔCOD
OB = OC Radius
OD = OD Common
∠ODB = ∠ODC = 90°
⇒ ΔBOD ≡ ΔDOC (By RWS Rule)
⇒ ∠BOD ≡ ∠DOC
∠BOD = ∠DOC = 85°
In ΔDOC,

∠DOC+∠ODC+∠DCO = 180°
85° + 90° +∠DCO = 180°
∠DCO = 180° − (85° + 90°)
∠DCO = 5°
⇒ ∠OCA = 70°
OA = OC = radius
∠OCA = ∠OAC = 70°