In ΔOAB,
AB = OA = OB = radius
∠ ΔOAB is an equilateral triangle.
Therefore, each interior angle of this triangle will be of 60°.
∠AOB = 60°
In cyclic quadrilateral ACBD,
∠ACB + ∠ADB = 180° (Opposite angle in cyclic quadrilateral)
∠ADB = 180° − 30° = 150°
Therefore, angle subtended by this chord at a point on the major arc and the minor arc are 30° and 150° respectively.