Now, join A and B to E.
AE is the radius of the circle with center A.
BE is the radius of the circle with center B.
AB is the side of the square.
We are given that radius is equal to the side of the square.
So, ΔABE is an equilateral triangle
⇒ Each angle of ΔABE is 60°. (All the angles of an equilateral triangle are 60°.)
⇒BAE = 60°