Answer:
see explanation
Step-by-step explanation:
∠ BOA = 360° - 250° = 110° ( sum of angles round a point )
∠ BDA is half the central angle, that is
∠ BDA = 0.5 × 110° = 55°
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The angle between a tangent and the radius at the point of contact is 90°, thus
∠ OBC = ∠ OAC = 90°
The sum of the interior angles of quadrilateral OACB = 360°, thus
∠ BCA = 360° - (90 + 90 + 110)° = 360° - 290° = 70°
