ABCD is a cyclic trapezium with AB || DC and AB = diameter

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ABCD is a cyclic trapezium with AB || DC and AB = diameter of the circle. If ∠CAB = 30°, then ∠ADC is

1. 60°
2. 120°
3. 150°
4. 30°

Correct Option: B

According to question , we draw a figure of cyclic trapezium ABCD

∠ACB = 90° (Angle of semi-circle)
∠CAB = 30°
∴ ∠CBA = 180°– 90° – 30° = 60°
Again, ∠ADC + ∠ABC = 180°
∴ ∠ADC = 180° – 60° = 120°