Two equal circles passes through the centres of each other and intersect each other at A and B. A line passes through point A intersecting the two circles at points C and D. How can I prove that the triangle formed by the points B,C and D is equilateral? O and I are the circumcenter and incenter of triangle ABC respectively. O lies in the interior of ABC and I lies on the circle passing through B,O and C . what is the magnitude of angle BAC?