Madhya Pradesh Police Exam Model Paper 5

Given:
O is the circumcentre inside the ΔDEF.
∠EOF = 150°
Concepts used:
The measure of the angle formed with the given base at circumcentre = 2 × vertex angle formed opposite to the same base
Calculation:
⇒ ∠EOF = 2 × ∠D
⇒ 150° = 2 × ∠D
⇒ ∠D = 150°/2
⇒ ∠D = 75°.
∴ The measure of vertex ∠D is 75°.