Question

.in a cyclic quadrilateral abcd ∠bcd=120° and passes through the centre of the circle. then ∠abd = ?

Answer 1

Given :∠ BCD= 120°

∠ ADB= 90° ( angle in the semi circle)

∠BCD+∠BAD= 180° ( opposite angles in a cyclic quadrilateral  is supplementary)
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∠ABD= 30°
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Hope this will help you...