OK, yet another geometry question. This one, frankly speaking, I don't know the answer also.
Here it goes:
Draw a circle with diameter AB.
On the diameter, mark a point C.
Draw a smaller circle within the big circle with diameter AC.
On the right of the small circle, draw a square such that the the centre of the square falls on the diameter AB of the big circle, the left edge is tangential to the small circle, and the 2 corners on the right falls on the circumference of the big circle.
Question: what should the ratio AC:AB be such that the area of the small circle equals the area of the square?
Please refer to the diagram below: