We have a triangle ABC with a circumscribed circle. Somewhere between BC we place a point D. There is a circle which goes through D and whose tangent at AB is A. This circle also intersects the circumscribed circle of ABC at a point E. Construct it.
So we're just going to construct a circle through points A and D, then see where it intersects ABC. So I originally thought that every point on the bisector of AD would work, but apparently not.
The answer sheet says that the center of the circle is the intersection of the bisector of AD and the line perpendicular to AB through the point A.
Why the perp line through A? I don't understand..