Given three concentric (having the same center) circles. Their radii are 1,2 and 3.
Place three points A,B,C - each on a different circle to get a triangle ABC with a maximal area.

What is this area?

(In reply to Another approach (spoiler) by Harry)

my solution has a slight mistake.  To compute the area of the triangle I used the coordinate matrix formula and in doing so forgot the 1/2 times the determinant and thus the reason why my area is twice yours. 

Posted by Daniel on 2010-09-11 22:37:01