UPSC CDS 1 2021 Math Paper

Given: △ABC is an equilateral
Concept used:
The angles subtended by an arc on the circumference on the same side of the arc are equal.
All the angles of the equilateral triangleare equal and the measure of each angle is 60∘.
Calculation:
△ABC is an equilateral
∠CAB=60∘
The angles subtended by an arc on the circumference on the same side of the arc are equal
∠CAB=∠CDB=60∘