If ABCD is a cyclic quadrilateral and ABC is an equilateral triangle find the angle of CDA.

Correct option is B

​Given:

ABCD is a cyclic quadrilateral.

△ABC is equilateral.

Concept Used:

Opposite angles of a cyclic quadrilateral are supplementary: ∠ABC+∠CDA=180^∘

Equilateral triangle: ∠ABC=60^∘

Solution:

By the cyclic quadrilateral property 

∠ABC + ∠CDA = 180^∘​ 

​$$60\degree+ \angle CDA = 180^0$$​​

​$$\angle CDA = 180^\circ - 60^\circ = 120^\circ$$​​