#### Question

In the given figure, AB is a diameter of the circle with centre O. DO is parallel to CB and ∠DCB = 120°.

Calculate : ∠DAB

Also show that the ΔAOD is an equilateral triangle .

#### Solution

ABCD is a cyclic quadrilateral

∴ ∠DCB + ∠DAB = 180°

(pair of opposite angles in a cyclic quadrilateral are supplementary)

⇒ ∠DAB =180° -120° = 60°

Is there an error in this question or solution?

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In the Given Figure, Ab is a Diameter of the Circle with Centre O. Do is Parallel to Cb and ∠Dcb = 120°. Calculate: ∠Dab, Also Show that the δAod is an Equilateral Concept: Arc and Chord Properties - Angle in a Semi-circle is a Right Angle.

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