Answer:
∠OAC = 27°
Step-by-step explanation:
The radius of the circle is perpendicular to the tangent line.
Therefore, ∠ACO = 90°
The interior angles of a triangle sum to 180°
⇒ ∠OAC + ∠ACO ∠ COA = 180°
⇒ ∠OAC + 90° + 63° = 180°
⇒ ∠OAC + 153° = 180°
⇒ ∠OAC = 180° - 153°
⇒ ∠OAC = 27°
