pls explain?

Question

In the euclidean plane,point A is on a circle centered at point O, and O is on a circle centered at A.The circles intersect at points B and C.What is the measure of angle BAC???

Answer 1

AO = AB = AC = BO = CO
so
BAO = 60°
OAC = 60°
BAC = 60° + 60° = 120°